I would love to make a basic coffee table that I could mosaic on top - but have no idea how to go about it. Are they websites that have step by step directions on how to make a table? Thanks

 

Visit Home Depot etc. And either purchase a piece of MDF or plywood to the size you want your table top. Then visit the molding section and grab 4 legs you like.
Get the metal hardware to attach the legs to you table while you are at it.
Then visit the tile area to see what depth of tile you wish to use and go back to the trim area to find some edge trim for your table top. OR you can use ceramic tile bullnose BUT that can get expensive. I prefer to use wood trim.
Go home and attach your legs to the table and paint and finish as you wish...add the wood trim, 45% miter cut the corners and again finish as your wish.
After this is all dry you now have a nice sturdy surface to do your mosaic on as well as a nice finished edge to work from so when you add your tile grout you do not have to worry about how to stop it falling off the edge.
This is about the cheapest way to make you own table next to buying a flea market find and adding the molding to mosaic the top.
Hope this helps get you started.
Rainie