"easy" "fast" and "best looking" tend not to play well together. Lots of people spend almost as much time on basing as they do on painting the mini, and it really is an art in itself. Personally I have a tendency to have a flash of inspiration for making a base, spend hours making it, and then hunt around looking for a mini to put on it.
I have 3 armies, all of which are based differently.
1) All my eldar are on sandy desert bases. (
http://s84.photobucket.com/albums/k20/me_in_japan/eldar/?action=view¤t=Jetbikes2.jpg) I used sand, glue, small bits of bark for stones, and the odd skull or bone to break it up. Then I painted them.
2) My nurgle are all on resin bases that I bought online (
http://s84.photobucket.com/albums/k20/me_in_japan/nurgle marines/?action=view¤t=Ndaemons.jpg). Website here: (
http://www.darkartstore.darkartminiatures.com/categories/THEMED-BASING/Infested/) This is a good time-saving solution to get an army looking uniform even if the minis dont.
3) My Dark Eldar are all on resin bases that I sculpted myself and then cast (
http://s84.photobucket.com/albums/k20/me_in_japan/Dark Eldar/?action=view¤t=bases2.jpg). The advantage of this is that it lets you bulk produce bases in a style completely of your choosing. I sculpted the bases uses milliput and threw in some details using eldar components. The disadvantage is that you have to fiddle about making moulds. Its not super tricky, though, once you get the hang of it.
In terms of practical advice for base building I'd say: Use height in the base to break it up and make a mini look bling (small rocks made from cork can be nice). Use light and colour on the base to draw attention to and complement the mini, and use different textures on the base (stone, grass, undergrowth, leaves, grasses, water) to make it interesting. This site (
http://www.necrotales.com/necroTutorials/) has some very good base making tutorials, and also anything Jarhead does tends to have fantastic basing - take a look at his gallery.
*edit* one possibly useful piece of info is that I tend to paint my resin bases all at the same time with an airbrush. Spray undercoat them with a spray can. Airbrush on the base colours (a bit of variation running through them is nice), then paint in the details. I did about 60 bases this way in a day. Then you can forget about them and go off and paint your minis. When the mini is done, your base is sitting ready to have the mini pinned and glued onto it. NOTE that this requires you to cut the tab off the mini before you start painting it. If you try to clip the tab off after paint has been applied, the paint will flake off around the minis legs from the shock of the cut. I learned this the hard way
