On the charms - you can attach them with a brad and make that feature on the card, or you can use twine or ribbon. I think it's hard to conceal whatever you use, better to make a feature of it. With ribbon you might need an extra jump ring (as you'd use in jewellery making) to let the charm lie flat. I see a lot of people adding charm in with their bows and I think it looks great - but I'm not much of a ribbon person on my own cards
. If I don't want to have to use anything like that I'll take a pliers and break the loop off, and just use glue.
Fixing wire to a card is easy if it's just a length of wire; use a fine needle or pin to poke a hole through the card, thread the wire through and fix it at the back with tape. Wire shapes without an end are harder, because you can't do this. A strong adhesive usually works, or else I'll actually sew them on with a couple of stitches in clear nylon thread if I can do this where it won't be seen.