How to land a skateboarding stair set?

I've been skating for about a year, and i can ollie a 4 stair. I've been trying to do bigger sets', like 6 or 7 stairs but I just cannot get it. Every time I land I either fall forward or don't land on the board. I need a strategy to be able to land a gap, jump or set pretty much the majority of the time. Thanks.