Mortal Kombat

What is the best strategy for combos?

I've played against people, I watched people online and I have to wonder. How do you guys get up to 20+ hit combos?! My longest string is 8 hits! Can someone give me some good advice to pull off long combos? It'd help a lot thanks.

Wow ok, thanks a lot. I'll see what I can do!

Either try and try until you get the right starter of your character and then see which specials/normals/combos keep the opponent in the juggle state and then finish it off with another damaging combo/special/normal/xray (generally speaking).
Or check out testyourmight.com.
There are more combos than one can perform, tips, guides, strategys, and more detailed info (mostly for competetive/tournament players) like frame data, comparisons, tier lists and matchups.