People usually prefer slowing the crystallization/nucleation rate, so you could try combinations of a cooler incubation setup (5C instead of RT), lowering protein and/or precipitant concentration, etc. 

I encountered twinning when crystallizing EpsG and had to do all of the above to slow it down enough, and even covered the reservoir solution in parafin oil (this was a hanging drop setup).

As a newcomer in protein crystallography you should launch your difficulies to the CCP4 Bulletin board. It is a platform for questions and answers for new, advanced and expert users in bio-crystallography. Also, you can look to earlier questions/answers, for example discussions on twinning.