Here's a little known sewing tip that will save you tons of hassle. Don't cut your patterns.
You know how you open up a pattern, especially a multi-sized one, and there are a bunch of different sizes all drawn on top of each other? Don't cut out the one you want to use. Trace it instead. I use a roll of white kraft paper I got from some paper store online to copy my patterns. If you live near civilization you could get some butcher paper from the local school supply store or paper store. Maybe even a butcher shop would sell you some. For small patterns I've traced the pattern pieces onto regular old white printer paper (sometimes I needed to tape two or more pieces of paper together). Just lay your white paper on top of your pattern and it should be thin enough to see the pattern lines through it. I've also used carbon paper under the pattern and traced onto tan kraft paper. This was definitely more complicated--just go with the white paper. I've also heard of people using non-woven interfacing for pattern tracing. Very sturdy, a bit more expensive.
I usually just lay it all out on the floor. If I had a fancy cutting table (like in my dreams) I'd lay it out there. I've taped some to the window so I could use the light to see through and trace (must have been using a thicker tracing paper on those).
You can kind of see in the picture the original pattern is on the right, under the kraft paper. A straightedge is usually handy when you're tracing patterns, and if you're using a paper roll you'll want something to keep the paper from rolling up while you're tracing.
Don't forget to mark what the piece is, how many to cut, grainlines, darts, and any other marks on the pattern piece.
Tracing your pattern serves a couple of purposes. First, it makes it so you can adjust your pattern pieces to fit you without messing up the original pattern. This is nice if you ever want to use that pattern to make something for someone else that's not quite your shape. I also don't feel bad at all cutting chunks out of my copies, but I would about doing it to the original pattern.
Tracing your pattern also usually makes it so you're working with a more durable pattern. Those tissue paper pattern pieces from patterns like Butterick and McCalls are especially obnoxious to work with.
And lastly, just because your kid is a size 4 now doesn't mean he'll always be a size 4! Tracing your pattern preserves the other sizes the pattern offers so you can sew more another time. Here's a pattern I got from my mom after she made a shirt for son when he was 4.
Of course she cut the pattern, crazy lady. But guess what? He's not 4 anymore. I've used this same pattern in a size 6 and 8/10 and today I traced off a size 12. Imagine what that pattern would look like if I tried to actually cut the pattern each time I wanted to make a different size! Yipes! I'd probably end up buying another pattern. So if you get a pattern that has been cut by your crazy mother, don't dismay--there's always tape.
Tape the cut out pieces back into the pattern and trace off the size you want to use. There's your first official sewing tip from me--Don't cut your patterns. It really is worth the time to trace them. :)