Hi.
There are no big secrets to mold making and casting.
First of all you will need to decide if you are going to make 1-part or 2-part mold. 1-part molds are the easiest and I do them constantly to make bases for Kits.
Best stuff I have found to make a box to make the mold in are LEGO bricks, yep, raid your tots toy-box.
What you will need:
non-drying Clay
vaseline
Silicon Rubber for mold making
Resin for casting
Rubber gloves
For both the Rubber and Resin try to get hold of stuff that mixes at a 1:1 ratio, easier that way and better results.
Next you will need to make a decision on Resin, they tend to come in different setting/curing times (faster = hotter) slower curing time also allows air bubbles to escape and thus get more into the fine detail areas.
There are a few sites online that detail the whole mold making and casting process or send me an e-mail and I can talk you through the trouble areas.