Scissors vs. x-acto is a matter of preference. I prefer working with a good, sharp pair of scissors, but some papercrafters argue that your lines won’t be as straight or accurate, and there may be some truth to that. In addition, there are pieces that are shaped in such a way that you’ll end up needing an x-acto knife to cut out middle portions or tight areas anyway. I always keep both on hand.
On most models, you’ll see three kinds of line: solid, dashed, and dot-dashed. Cut the solid lines, mountain-fold the dashed, and valley-fold the dot-dashed. (If what I mean by mountain- and valley-folds are unclear, you can Google it for pictures and explanations.) If you’re working with Pepakura, be aware that not all solid lines need to be cut. See below.
After you’ve cut out a piece, it is very helpful to take the x-acto knife and lightly score each dashed/dot-dashed line (and any solid lines that were unnecessary to cut). This makes it easier to fold (particularly the mountain folds) and helps to keep those folds straight. If you have a particularly stubborn valley fold, you can try scoring the back side, though it’s often hard to line up exactly.
Some papercrafters use “the smooth technique” where they don’t actually score or fold the pieces and try to attach them so that you end up with curves rather than sharp edges for the most part. You can try it with various models to see if it works with them and your style. Sometimes it works, and sometimes it doesn’t.
Some people cut everything out and then assemble it. I sometimes find it hard to keep track of all the pieces this way, so I went with cutting out one piece, assembling it, and cutting out the next. I typically have a movie on in the background to keep myself sane while this is going on.
In really tight spaces, I sometimes use the x-acto knife as a tool for getting glue where my fingers don’t want to go. Other times, the flat edge can be useful as a place to put pressure on when you’re trying to hold pieces together while the glue dries. Just be careful not to cut yourself, and clean the blade if it’s getting dried gunk on it.
Notes on Pepakura
If you’ve got a .pdo file and don’t know what to do with it, you’ll need to download Pepakura, a software for turning models into papercraft: http://www.tamasoft.co.jp/pepakura-en/
Play around to get used to using the Pepakura software before getting started. The controls aren’t obvious:
No keys, right mouse: rotate model, pan pages
Shift, right mouse: zoom in/out both
CTRL, right mouse: pan model, pan pages
If you have a mouse wheel, that will can also zoom or pan. You can also right click on the model to change the center of rotation (choose the option, then click on the model where you want the new center to be).
Clicking on a piece or model will select it and lighten all others. You can shift-click to select on multiple pieces, which I find to be a handy way of keeping track of what I’d cut out and assembled.
When you hover the mouse over an edge on the pages, it should highlight the edge and create a red line showing where it connects, either to another piece or to a different edge on the same piece.
Not all solid lines actually need to be cut (I butchered my first project because I didn’t realize this). Sometimes things are very nearly connected, but not quite, but the software wants perfection, which is just not possible. If you zoom in far enough on some solid lines, you’ll see that it expects you to cut it and then reattach it with a tiny tab. I find this so unreasonable that I don’t cut these and just treat them like folds. Keep an eye out for these kinds of spots where it looks like maybe you don’t actually need to cut there.