Professor Lam is by far the most thorough, caring professor in the department of chemistry at UCLA. His notes, his slides, and his practice problems are done with care, and with the student in mind. Office hours are fantastic, as you can see he loves the field of organic chemistry. Exams are some of the most challenging amongst all of the instructors in the dept. of chemistry, but they are fair, thorough, and well-thought out. He really wants you to learn, and supplants the grading scheme with some helpful curving. I am a graduate student now, studying organic chemistry, and I still go to Lam's VOH page to quickly review notes and what-not.

I would give Lam the highest recommendation for those who want to actually learn about chem, not just want an A-grade.

Professor Colin Lam is one of the best, if not the best, professors I've had here at UCLA. He knows what he's talking about, but what's even more important is that he can communicate all his knowledge effectively to his students. He can make what at first seems like an absolutely crazy reaction mechanism look easy. He always has a smile on his face and cracks jokes from time to time, making going to class and listening to lecture a joy.
Like other reviewers have already said he always posts tons of extra information online to try and help the students out in anyway he can. He also holds office hours and will stay well past their scheduled time slot until all questions are answered. He is completely devoted to making sure his students learn the material, and you can tell he love what he does.
However, his exams are tough. You may know the information, but if you haven't mastered the stuff, you won't have time to try to rationalize the mechanisms, etc. 50 minutes for his midterms is never enough time. But in the end, if you work hard, and if you manage to pull off an A, it'll be one of the sweetest A's you'll ever achieve at UCLA.
I'll quote one of the fellow evaluators by saying "Consider yourself very lucky if you ever have Professor Lam!"

Professor Lam might be a little difficult to understand at first, but he speaks very good english and it's easy to get used to his accent. While the textbook tends to skim over the more difficult topics, he uses the lecture slides and course reader explain those topics in depth instead of reiterating what's in the book. He posts plenty of practice material online, and there's even more practice in the course reader although I didn't have time to do it, he goes over pracice exams at the revew sessions, and I'm not sure what he does at office hours because I never went. For someone so young, Professor Lam is a very confident and organized lecturer. Sure, his test averages are low (final was 52%) but if you're smart and study hard you'll ace the class.

Professor Lam is hands down amazing. The very first time you see him you might mistake him for a TA, because he looks so young. He knows all the topics by heart, and has the amazing talent of processing and communicating his ideas both quickly and clearly. After the first day of lecture, you will understand what I mean.
He is very nice, humble, and approachable, and he will hands down help you in anyway possible. He has a lot of practice materials, he's willing to continue to hold office hours long after they are over, and he always holds review sessions. One can treat him as a friend, but remember to respect him as a professor too! Oh yeah, he will definitely make the effort to remember you if you meet him.
His tests are very fair (seems like previous tests were much harder). However, the midterms are very time pressed. That means even if you know the material, if you didn't master it, you probably won't finish. Try your best to glance over the slides before class!
I can tell that professor Lam loves organic chemistry and he loves teaching too. Consider yourself very lucky if you ever have professor Lam, and work hard!

Oh, Prof. Lam! I was pretty devastated after taking my first midterm (knew nothing and the class average was in the high 20s-low 30s) but he held a workshop for us to go over the midterm and the second midterm was much more doable. He goes at a good pace and is very clear in his teaching style. I'll echo another reviewer in saying he is the best o-chem professor I've had.

Dr. Lam is a very knowledgable professor. He knows his stuff very very well and is willing to help students during office hours and answer their questions. The two workshops he held were very helpful in terms of understanding the concepts of organic chemistry. I strongly recommend people to take his class because although his exams can be hard (the Oxford standard), they help you learn. Since the class is curved, as long as you place above average you will have an A or a B. Despite the low marks on my two midterms, he is so far the best organic chemistry professor I have ever had.

Professor Lam is a very dedicated professors. He held two workshops on Saturday to strengthen our understanding of substitution and elimination reactions and NMR spectroscopy.
His tests are hard. He tests stuffs that he only slightly went over in class (ex. he tested us on mechanism of NAD+...) However, he curves nicely. So, don't worry if you got a bad score on the test. Most people will do horrible too :]
He posts very good handouts and slides on VOH. So, don't worry too much if you fall asleep in his class. It's easy to fall asleep in his class. I think he tries to keep us awake by putting funny things in slides (ex. he did animation of bad mechanism arrows burnt in fire.)
He is very helpful in office hours. You can ask him to make up problems in office hours, and the problems he made up are hard and help you understand the concepts a lot better. I really like professor Lam. I hope he will stay in UCLA.