Sewing snaps is a bit of a pain but I found some tips that make it easier for me that I wanted to share. 
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Tools and materials needed: item in need of snaps, snaps, a sewing needle, thread, scissors and a seem ripper or something to remove stitches in case you mess up. lol
* I use a double threaded needle with a knotted end.
* I do 3 stitches x2 per snap half, top and bottom per side, so 6 stitches in total for each, and 12 stitches total for each snap x2.
* I sew the thin snap at the top first on the inner and the heavier snap at the bottom on the outer.
* If I have to do more than one snap I sew the all the thin sides first then the other heavy side next so I can better match them up. You can use pins to help you with that.
* I do 3 stitches x2 per snap half, top and bottom per side, so 6 stitches in total for each, and 12 stitches total for each snap x2.
* I sew the thin snap at the top first on the inner and the heavier snap at the bottom on the outer.
* If I have to do more than one snap I sew the all the thin sides first then the other heavy side next so I can better match them up. You can use pins to help you with that.
Hope that will come in handy!
Annablythedoll xo