You need to make sure and top the mold off. Hollow heads = sucking in air vs. plastic.
Jason
Yep. What Jason said. Also, hold pressure on the injector for a ten count or so after it stops, then let the pressure off and lift the injector. Hold the injector above the sprue and let the thin stream that drizzles out top off the sprue until you get a small puddle at the top.
The cooler you can inject the less shrinkage you'll have. Try heating your plastic to 350 then letting it cool to around 320 or so before you inject. With the exception of ribbontail worms, all my molds shoot perfectly in the 310-320 range.
Like pjmcla said, The search engine is your friend. There's tons of great info on many topics that've been covered on here. That being said, If you can't find the answer to your problem in a search, don't hesitate to ask. It's very much a family atmosphere around here, and there are plenty of talented people here who are happy to help. Welcome aboard.
