Crocheted button loops are a favourite of mine. I like the fact that I can add them after a cardigan or jacket is otherwise completed; the decision about where to place them can wait until I see how the garment hangs on its intended victim. Likewise, I don't have to make a final decision on the actual buttons until the knitting is over. If you'd like to try out these button loops, here's how to make them. I generally use a crochet hook two sizes smaller than the needle size used for the body of the garment.
Button Loops
With WS facing, join yarn by pulling a loop through the front edge, ch 3, sl st into edge, ch 1, turn, 5 sc into centre of loop, then sl st into spot where yarn was joined (but from RS this time). Cut yarn, leaving an end long enough to thread back through the loop for added firmness.
You can experiment if necessary to change the size of the loop to fit your buttons.