Well - density is density: objects per unit area/volume. 1:10 dilutions (one part in ten total) are 1 part stock with 9 parts solvent, other common ones are 1:2 and half-log.
It depends a bit on how good your biology is as to what level of guide you need. I would suggest getting a good textbook on your particular field of biology to get started.
In terms of techniques:
Molecular cloning: a laboratory manual (Sambrook et al) is a great resource, but probably overly technical for what you need. Covers all of molecular biology with detailed protocols, also includes such things as western blotting and the likes.
Culture of Animal Cells: a laboratory manual (Freshney) is excellent for animal cell culture
Current Protocols (many different topics covered - check your library's catalogue), has excellent detailed protocols and background.
Nature protocols: detailed, but often difficult protocols, mostly designed to overcome particular difficulties with individual techniques (at least in the ones I have used, but I generally only need them for specific things, not the basics).
Many manufacturer websites have excellent resources too. I particularly like Roche LAB FAQs (they have an app as well as pdf/booklet) for basic formulae, and as a quick reference. Abcam usually has good stuff for protein blotting and the likes. Amersham/GE is excellent for protein chromatography. Just have a look around, you'll often find the basics hidden away under the "documentation" or "resources" pages.