I use double-sided Scotch tape for a good portion of my scrapbooking projects because it's cheaper than continuously buying tape runner refills, but recently I started using a glue pen for papers, which seems to work even better than the tape, and things lay flatter.
I like Zig Memory System's 2way Glue for flat stuff and Tombo Mono Aqua Liquid Glue for flat and 3d embellishments. Occasionally I use Provo Craft Terrifically Tacky strip tape for paper on cardboard, but I generally save that for ribbon and embellishments that need a solid tacking down.
I'm not always good at planning ahead on my LOs and cards and albums but I try not to let brads and eyelets show through the other side (unless the eyelet hole is perfunctory). Sometimes you can't help it, and then you just find something cute to cover it with!