The major problem with tomato seeds is that they are encased with in a gel pack to prevent premature germination within the tomato.

After cutting in half and scooping out the insides and getting the seeds out. 

Separate the seeds from any fleshy bit of the tomato.

Add water and place in an air tight  container for 5-7 days. After which ? I will let you know. Youtube videos say that the gel pack surrounding the seed will have been removed from the seed.

 

After 7 days the contents was emptied into a sieve, any fleshy tomato was removed and the seeds allowed to dry on COFFEE FILTER paper. Most seeds do not stick to this paper and when dry can easily be brushed off into either dry jar for long term storage or into propagator for germination.

Placing a few seeds on kitchen paper and left in a plastic food container, nearly a week later most of the seeds have germinated.  In a few days they will be ready to plant out in pots.

Van Heijningenn tomato nursery