how to un-partitioning drive

Can someone please help. A year ago I partitioned my drive in anticipation of installing the yet to be released Lion on one partition and keeping snow leopard on the other. I had never gotten around to installing Lion - but am about to know and no longer want the partitions. I want to revert back to just the single one partition that is currently running snow leopard. I then will install Lion on top of SL.

Easy step by step instructions would be greatly appreciated!!

Thanks in advance,

Rob

PS - I'd reverse everything I did when I partitioned but can't remember how that went down.