First of all, practice! Practice and experience are probably your biggest hopes for getting better. Everyone will have their own quirks and techniques.
Other than that, fortify archery enchantments/alchemy effects boost your damage, and relevant perks can further boost your damage and zoom in your sight and slow time slightly to give you a better chance (don't use these too much though, or you'll stunt your own growth). Aim for the chest if you're close, and for the head if you're far away, 'lead' your target (ie shoot slightly in front of a moving target, taking distance and their speed into account).
The Slow Time shout can give you the opportunity to loose a whole barrage of arrows before the first one even hits its mark, so that's another thing to consider.
There's more, but I can't think at the minute, it's late here.