I am a first time seeder and I am trying to save the seeds from the fruits and vegetables I consume so I can plant them later. I understand how to properly save most seeds like. However, I am unsure how to properly seed a tomato. How should I go about seeding a tomato?
A great reference on seed saving for many common (and some rather uncommon) vegetable crops is "Seed to Seed" by Suzanne Ashworth. You can find tomatoes starting on p156. The info below is cribbed from this book and other sources. (Note that saving tomato seeds is a bit more involved than many other vegetables, some of which are trivial to save, like peas or beans.)
If you are trying to save your own seeds indefinitely (i.e. without refreshing from another source), you'd want to save seeds from at least 20 different plants of the same variety.
With modern varieties, you may not have to worry about isolation because they don't tend to cross. If you want to be sure about avoiding crossing, you can cage them to avoid insect crossing.
Tomato seeds need to ferment before they are viable. You'll need to help this fermentation along. Squeeze the seeds and tomato "goo" into a small bucket -- a 32oz yogurt container, deli tub, or similar container. Be sure to label the tubs. After a few days it will smell bad and grow a layer of mold over the top. (You'll want to have the bucket in a place where it won't get tipped over...) At this point, add more water, swish it around, and then let it settle for a moment. The good seeds will be at the bottom. You can skim off the top, or just pour the whole mess through a fine strainer. Rinse. "Seed to Seed" suggests putting the good seeds on a paper coffee filter; cloth or paper towels are a bad idea because it will be really hard to remove the seeds when they are dry. Let the seeds air-dry in dark place, stirring regularly. If they stay damp they may start to germinate.
See also this answer in gardening.SE about saving seeds in general; that answer has a link to info that is specific to tomatoes.