i always get these two mixed up. which one is which, and what are the distinguishing characteristics of each?

I can only offer a little bit of general information.

Hung Gar

Progenitor Hung Hsi Kwan, Shaolin monk Southern temple. Learned Long hand from Chee Sin and short hand from Fong Chuen. The art evolved overtime on the boats of south China. It is the hardest of the hard styles. Characterized by low stance work and power development. Top form in the system is Taming the Tiger. Most advanced strength exercise is Iron Thread. Very curious that such an external style has an internal exercise like this.

Choy Li Fut

Each a system in itself, Choy Li Fut is a combination of the three. The progenitors all Shaolin monks from the south temple. Li Yao Shan, Choy Fak and Wang Shan. Li style is characterized by hand techniques. Choy Gar has foot techniques, meaning foot work, stances and legbreaking techniques. Fut Gar is Buddha Style. This combination occurred over 100 years of evolving and blending.

The green grass monks came out of Choy Li Fut, they were Hing Sing and Bak Sing.

As far as distinguishing one from the other, they are both southern systems so my guess it would be difficult to do.

Hung Gar is alot more linear in their techniques. Almost like karate.
Choy Lay Fut is alot more circular. They tend to send swinging like attacks more than linear attacks. Both have their advantages and disadvantages. The only Cho Lay Fut teacher I would recomend is Doc Fai Wong. As for Hung Gar I would say Wing Lam? I dont know about other instructors though?

If lineage is a question, would students of Doc Fai Wong be acceptable as instructors? There is a string of studios in So Cal called White Dragon. I studied Choi Li Fut briefly under one of the former teachers in training since hes extended family and roomate at the time.

His teachers Payne and Fischer were (I thought) students of Doc Fai Wong. They seemed pretty knowledgeable. This was when there was only one WD studio (about 17yrs ago??) Now, they seem to be everywhere.

My friend resigned his teaching position to go back to school, and I cant vouch for the other teachers I've never seen in action, but those two Payne and Fischer having studied under Doc seemed very, very, capable.

Mmm Chou Gar the best of both worlds!

Doc Fai Wong looks prett good for Choi Li Fut but if your in San Francisco...so many options. He never struck me as much of a fighter anyways. Solid skills but hardly the best available. And how could you mention Wing Lam and San Francisco in the same breath for Hung Gar. The one and only, the great and amazing, adpoted nephew of Grandmaster Lum Jo himself...Y.C. Wong stills runs his humble Hung Gar school in a basement in Chinatown there.

I have spent so much time with both of these styles I find it hard to imagine getting them confused, unless you just can't tell which one is called which name. Hung Gar is ultra-classical southern gong-fu. Choi Li Fut has a much more northern flavor. I trained Hung for 8 years and most of my MA training friends in that period were Choi Li Fut guys. They use a lot of leopard fist and just plain leopard style techniues. Choi Li Fut has endless hadn forms. Hung Gar has maybe a dozen but really only 4 or 5 that are core to the system. And yes, the last form Tit Sin (iron wire) is generally a pretty closely guarded seceret and looks almost purely internal. It's like a breathing and dynamic tension set. It builds a tremendous 'iron shirt'.

Hung Gar is structured on a system of 5 animals and 5 elements. My schools website says, "The Dragon, Snake, Tiger, Leopard and Crane are said to give the practitioner five ways to manipulate and use his strength while the Wood, Fire, Gold, Water and Earth elements are said to give him five ways to generate and transform the power in each of these forms."

But in practice we tend to use mostly a combinatain of tiger and crane techniques, hence the nickname for the style, 'tiger-crane'. In higher level players you might see more dragon. The iron wire set is a 'dragon' style form. As there obviously arent'any dragons around to emulate, this drives home the point that what we learn from the animals is not how to use our non-existent claws and wings and such but rather certain other less tangible qualitires. In the simplist terms tiger+crane = strength + agility.

Choi Li Fut I know much less about.

Omar pretty much nailed it on Hung Gar, as did other people. CLF people tend to do very circular attacks, and Hung Gar more direct. It took me a while (though even I do get confused on occasion) to distinguish the 2 when I see a video of it in action. My best bet is to find some good CLF and Hung Gar clips online and watch them, you'll see the difference. I have some good clips from both styles on my PC, sadly I can't remember where I got them.

Hung Gar is famous for its snake and crane form. It forms its base on animalistic forms with lots of low stances using power with force. This form was founded by a Chinese rebel named Hung Sing Kwan or Hung Hei Gwoon. But the most famous one of all would be Wong Fei Hung, then Lam Sai Wing, Kwan Tak Hing, Lam Ji Cho ( Lam Sai Wing's son), and Wong Kiew Kit ( Wong Fei Hung's father). Omar sums up Hung Kuen. I on the other hand will sum up Choy Lay Fut.

Choy Lee Fut was founded by three men, Choy, Lee, and Kwan. This system actually has both northern kicks and southern fist. But to distinguish them, there is Bak Sing and Hung Sing - Northern and Southern Choy Lee Fut. Northern emphasizes more on their kicks while southern emphasizes more on the fists. I will be mostly talking about Hung Sing Choy Lee Fut, which is what style I originally learned. Choy Lee Fut is a derivative of Hung Kuen or Hung Ga with northern elements, Our stances may be a little different. We believe in a circular motion of fists and kicks. Our punches are more like a iron ball and chain. You swing a chain and get hit by a iron ball. Our famous set or first set is Sup Ji Kuen - 10 Fist Form. We have three types of fists that are very famous as Choy Lee Fut, and they are Gwa, Sow, Tsop. This alone differiatiates Choy Lee Fut and Hung Kuen. Both of these systems are very famous in Canton and have a very long line of bad blood. In Chinese New Year - there is lion dance that we do which is to compete against Hung Kuen. Choy Lee Fut and Hung Kuen have had battles but are the most famous ma in Southern China.
Schools that teach Choy Lee Fut in LA are Buk Sam Kong, and Ng Fu Hang. Buk Sam Kong mainly teaches Hung Kuen but does know some sets of Choy Lee Fut. Ng Sifu, is the head founder of Choy Lee Fut in Hong Kong. He is based in Arcadia. He can tell you what schools are there in your area and what they are known for. I was taught under Howard Yee Lee who was taught by the late Lau Bun in San Fransisco.

I mean Chan Yuen Wo not Kwan.

correction: tiger and crane form. That's the one Huang Fei Hung invented.

Yea, my bad. I was up too early.

Ok, there's been a lot of myth and mistake here regarding CLF. CLF was founded in 1836 by Chan Heung in King Mui Village, Toisan County, Guandong province. Chan Heung intitially learned Nan Sil Lum Hung Men Kuen from his uncle Chan Yuen Woo from the age of 8. Chan learned rapidly, and in his early teens his uncle sent him to train with his Sihing, Li Yao San. Li Yao San was the founder of the Li Gar system, one of the 5 families of southern Shaolin. Over the course of 10 years Chan learned the entire Li Gar system. Li then sent him out to find Choy Fook, AKA the green grass monk. After eventually persuading Choy to take him on as a student, Chan learned northern shaolin and Lohan Qigong from him.
In 1836 Chan returned to King Mui and opened up his school, the Hung Sing school (from this point referred to as Chan Hung Sing lineage). One of Chan Heung's top students, Jeong Yim was sent to Futsan to run a Choy Li Fut school there. Jeong's system evolved, placing great emphasis on long arm power. This line is now referred to as Jeong Hung Sing. One of Jeong's descendents, Tam Sam, established a school in Kwongchow, but later moved to Hong Kong. Here he met and befriended the Northern Shaolin Master Ku Yeo Cheung (Wing Lam's Sigung). This led to an exchange of ideas and students which led to the development of the Bak Sing Lineage (also known as Bak Sing Fut Gar).
It would be innacurrate to say that CLF is reliant on expansive circular techniques. Indeed, as has already been mentioned, a stabbing, linear leopard fist punch is a hallmark of the style. It does express full extension more than Hung Gar, and the footwork is more agile and dynamic, but the two are clearly related. Close range techniques are emphasised just as much as the long (if not more) and sticky hands is a fundamental part of training.