My favourite slip stitch pattern goes something like this:
CO 2n+1 st
*p1*
*k1 s1* k1
*k1 ybf s1 yfb* k1
*k1*

This pattern is half stockingette stitch, with slipped stitches spanning three rows and a great square pattern on the back.

Now, as far as right-leaning decreases go, you can’t go past k2tog, so I’m using that, but I’ve had some trouble finding a left-leaning one that I like. I was using plain ssk, but have found this new method that I like much better.

The Improved ssk
Slip 1 stitch knitwise
Insert left needle into front loop of stitch on right needle
Insert right needle into back loop of stitch on left needle
Knit them together!

This is essentially the same process as a classic ssk, but the second stitch is slipped purlwise as you insert the other needle. Because there’s less mucking around, the stitch is tighter, neater, and lies a little flatter than ssk as well!