First, and don't laugh, you need to remove everything from the garage. It sounds funny and obvious, but have you seen how full some people's garages are? It may be a whopper sized commitment to remove all that stuff, and when you take it out, where are you going to put it. The simple fact is that you can't do a good job doing little sections and moving stuff from here to there, so take it all out.

Next, you need to clean, clean, clean. This means sweep, then vacuum, then wash until the floor is really good and clean. If you have oil stains, you may need to try some different cleansers and get as much of the stain removed as possible. Some detergents will actually help to open the pores in the concrete so that you can suck more of the oil out. Also, a little kitty litter or laundry detergent goes a long way. Pour them on the stains and let them sit a couple of days, then vacuum them up and scrub the area with soap and water. When it's all clean and really dry, you're ready for the next step.

Time to visit your local home improvement store. Carefully consider the priming options available to you when painting concrete. And if you want paint or stain. There are various products that help to prime your concrete to hold paint. Most of them in some way open the pores of the concrete so that more paint soaks in. Some of them are specifically for paint and some are specifically for stain. Read carefully or consult with an expert because you don't want to get the wrong one for your purpose. Also, check your paint or stain to see if they already have that product built in. Check them to make sure that they will be able to cover and stick over any oils or other substances that you've spilled on the concrete and been unable to remove. Last, make sure that you get one that will repel any future spills.

When you paint the floor, make it easy on yourself and get a long handled roller, preferably one that will take a little pressure. Make sure that the section that screws into the roller handle is metal and not plastic. If it's adjustable it is all the better because you can avoid a sore back by adjusting the handle for your height. Another helpful gadget is the long handled roller that has a tube built into the handle. As you paint you push the tube forward adding more paint to the roller and saving yourself time going back and forth to the roller tray. Of course, in that line of equipment there is also one that has a tube that runs to the bucket to keep up a steady flow of paint, but you do have to move the bucket frequently and watch the tube to make sure it doesn't drag in the wet paint. Be sure to put on several light coats, allowing plenty of time to dry between each coat. Unlike walls or ceilings, this is one area where if you get just a little too much on a coat, you won't have drips to worry about, but you will have to wait longer for it to dry so that you can get all your stuff back in the garage!