what is exact flow?

Question

 hi,

  we all know SDLC . But unfortunately  in my total carrier of 4 yr i didn't realize this concept.

  and one more thing i am working in very small company they don't have such time to sit    design  database , gather perfect requirement. Every time they apply temporary path to probleam. I am from last 2.5 yr developing ERP that was still not approved by client. 

 every time i am told him please be specific in requirement last time it changes.

So, basic question are 

 1) is best that every S/W company must have client agreement that can show that this is final  requirements.(special only one client)

 2)what was exact flow that very small company must obey for great future.

 3)is database really play most important role in successful project?

  

 in short provide me proper guidelines so my company will grow fast.

please need practical answer .

I am sr. developer in my very small company