Most of us will tend to setup our seed growing operation in the basement or some other out of the way location.  These are probably not the warmest spots in our homes.  We need to supply some extra heat. The best solution is a heat mat that is designed for the purpose.  It’s water proof and has a thermostat (to avoid actually cooking the seeds). Your tomato seeds would like a soil temperature around 75 F / 24 C and are quite happy if the air is several degrees cooler.

For the vast majority of our seedlings, ordinary fluorescent light will be more than sufficient. Keeping the tubes within an inch or two of your plants is the big secret to success. This requires some method of adjustment so that the distance can change as the plants grow.