check out the combo threads (there's a couple) in the SAVED THREADS option on this Q&A and there's a lot listed, but most of what has been said above is what you should do, keep combos simple and short. Long chains are for when your opp is hurt and you're trying to flurry to put him down.

With kicking combinations start with a push kick to get their weight moving backwards, like the one Skpotamus said.

With knees, I like to grab them first...e.g. lead hand jab, reach behind their head with my rear hand, then rear knee.

I don't really think more than 3 hits ahead, mainly because I'm crap, but also because after say a jab/cross/round kick they would have reacted, so I need to change my plans.

Without getting into the minor pissing match that got started... LOL

I approach combinations like this:

I teach only SIMPLE combinations. Two to three striking techniques only. RARELY, I will teach a four-strike combination. Defensive techniques are sometimes added as "extras". It is my feeling that simple combinations are really all that matters. Longer, advanced combinations are merely extensions or combinations of simple combinations. To be a successful fighter, you must learn to "flesh out" the simple combinations and turn them into advanced combinations on your own.

For instance, lets look at a few really simple combo's...

1. Double Jab (yes, this counts as a simple combination)

2. Jab-Cross

3. Cross-Round Kick

4. Round Kick-Push Kick

There you go! Four simple combinations that every fighter should know. I teach combinations like those above in my class constantly. But then I will occassionally have a lesson where I introduce my students to combining simple combinations into advanced combinations. For instance, using the above example....

Double Jab-Cross-Round Kick-Push Kick

I have just strung the four simple combinations into one long combination. You can flesh this combination out further by adding defensive head motions and footwork to change the angle of attack.

Also, in respect to combinations, I never tell ANYONE (be it a student of mine, someone else's, or merely an observer) that a combination WON'T WORK. How the hell would I know? What makes a combination work is PRACTICE! If you think of a combination (now matter how impractical it may seem to an observer) but practice with it on the pads, heavy bag, and finally while sparring, you can MAKE IT WORK! The key is that if you practice it with REALISM, you can fine-tune it and make the adjustments that will lead to success.

So, whenever a student of mine asks me, "Will [X] combination work?", I tell them, "Go practice it and them come back and tell me yourself."

Khun Kao

Great advice Khun Kao, my pad work includes some similar combos.
Left roundhouse, right cross
Right roundhouse, left hook

Where I train we spar more than we do pads. The first thing I was tought was "anything more than 3 hits wont work and you'll get hurt". It has proven to be 100% true in my experience.

What I practice and use is mostly 3 and some 4 hit combos. If you still have the advantage after your first combo, keep adding more 2 and 3 strike combos. Why work on learning some insane 15 strike combo you will probably never find the opportunity to use (except in video games). I would recomend MASTERING smaller combos and blending them together when the opportunity arrises. Once you master the obvious ones start working on specific short, med and long range combos so that you can easily transistion from one to another.

This is what works for me. For me, this makes most of my combos run almost by insinct. If I tried to leard a bunch of complicated or long ones I would spend to much time thinking instead of fighting.

Hey thanks to all who wrote.. I have to say that I did get pissed off and I pissed off other people also. However I know that basics are most important when sparring or training, as well with shorter combos, but I was just throwing up wild ideas in the air. Hey get don't pissed at me, I'm stating my free right of speech. Thanks again!!!

Brooks hit it right on the head. Whatever works is whatever is open at that moment.