Just like there are different types of kisses, there are different types of hugs. A parent hugging her child is not the same as a man hugging his girlfriend at the end of the date. It's usually a safe to hug in public, so it's a nice way to show affection to a special someone no matter where you are.
Relax yourself and attempt to do the same for the person you want to hug. Nice conversation and some laughs can take your mind off any nervous jitters.
Steady your breathing so you don't heave in your hugging partner's ear. It's also a plus if you're not sweating profusely during a hug.
Move slowly toward your special someone while looking at her face, especially her eyes. Get close together and lean in with your arms and upper body. Get comfortable in your hugging partner's arms and make sure they are comfortable too.
Move your arms smoothly, not in any jerking movements, around your partner's back. While rubbing him gently, you can whisper nice things in his ears. Appropriate topics include his attractive appearance, soft skin or nice scent.
Pull away slowly and gently. Smile when you pull back so she will know you liked the romantic hug.
If you sense hesitance, maybe a handshake would suffice for the moment.
Be sure the urge to hug is mutual. Nothing is less romantic catching someone off guard with a hug and watching him pull back with a shocked face. Try friendly hugs at first. If he reacts to side hugs and slight squeezes with smiles, it's probably safe to proceed to hugging romantically.