I started with a seed heating mat. My garage is normally 40-60* which is too cold for seeds to germinate. The heating mat draws just 17w and is able to warm the soil by 10-20*.
Next I got a plastic bin and filled it with soil. I was concerned that the heating mat wouldn't be able to heat the amount of soil that I was using, but it did just fine. After 24 hours or so, the surface of the soil was warm to the touch. I keep the lid on to help retain the heat.
In this container I planted 3 different types of tomatoes, green peppers, and Brussels sprouts. Once the seeds sprout I'll have to get grow lights over them until they are big enough to be potted up.
For now my grow lights are being used on my herbs. I threw some dill and basil seeds in a container maybe 2 weeks ago and left it in our bathroom. I left it in the bathroom because it was warm in there. Once the seeds sprouted I moved the container to the garage and put the grow lights on it. The two longer lights came from Walmart and were $10 each. I highly recommend them. The shorter light was more expensive and came from Lowes. The Walmart lights are a better deal.
Once these herbs get a little more established they'll be moved outside.
The final thing I need to note are my pepper seedlings. I planted pepper seeds on Jan 1. Only two of them sprouted. I used the container with the blue lid above, and the heat mat. I'm not sure why more of them didn't make it. Regardless, I moved the two that did sprout to bigger pots.
Then I put them up on a box and got them right under my 4' T8 shop lights. They seem to be doing OK there so far.
Here's a wider shot of the entire setup.
There's one other thing to note. I have the grow lights on a timer. I like to automate things as much as possible.