If you don't have it, get the tinker skill too. Holy crap is it a relief to not have to agonize over which modifications you're going to put where. I wasn't too happy at first about the skill that lets you pick up traps and tripwires that you need to get first, but I've found myself using it a ton too, so it turns out that going for tinker has some great side benefits as well.
Edit: Also, I'm starting to get a feel for certain things in the game that were once a mystery to me. For instance, early on I wondered why there were so many slots for weapons when they weren't dropped as items or found anywhere except for from vendors. Now that I realize that ammo types and modifications are basically the only things that really affect performance, I know why. Ultimately I'm going to need a separate weapon for almost every ammo type with modifications tailored to that specific ammo type, i.e. Two Hunter bows, one with fire mods and one with damage mods, possibly another with tear mods, Two sharpshot bows, one with damage, and one with tear mods, and so on. Furthermore, I'm going to need several sets of armor with different mods in each as well, though I haven't examined those as closely as weapons yet.
