Several things to for a really, really great blow-job:
1. Tease first, delay sucking. Fast and furious can cum later
2. Watching a BL is sensual. Make sure no hair is in the way. Get a hair tie.
3. Make authentic noises. moans, dirty talking...but no fake porn stiff...the noise, moans, tak should come from your heart.
4. Keep eye contact. that's a real turn-on
5. MOST IMPORTANT: Enjoy yourself and make sure he knows that you are enjoying yourself...not just going thru the motions.