as fiona said - brads are really just paper fasteners - so dead easy to use- I have found if you make a little hole with your knife first then it is easier to push them through. They are also very cheap - a good place to start with if you like this look.
Eyelets - I have bought some eyelets and a kit, but so far i am not that impressed. You need an 'anywhere hole punch' which is a tool that you hit with a hammer and it will punch a hole anywhere in your paper (whereas a normal hole punch will only reach a couple of inches from the edge).
Then you get an eyelet - put it through the hole and turn the paper over, so it is upside, with eyelet sticking up - you use another tool 'eyelet setter' and bash it with a hammer and it bends all the sides of the eyelets over so it is secure - the trouble I have is that my eyelets always end up looking very bashed. I think it might be because I bought a very cheap set of eyelet tools.
eyelets come in all sorts of fantastic finishes and they can look quite smart - I quite like when they are used for the holes in letters - especially since cutting out the center of letters is so fiddly. You can buy a big box with 100's of eyelets in various colours from Artbase for £20, or you can buy tiny bags of 10 eyelets for 50p from Scraptastic. I have just bought a few bags of eyelets in a couple of colours to get started with.
the thing to remember about Scraptastic is that there website is never up-to-date, they have loads of stuff which isn't listed, so you need to call them.
Bev