Seed starting is more than just the "dirt". I sucked at germinating until I found the right combination for the way I do things, my climate, my window orientation, and so on. I can start pretty much anything in pure peat, warm temps, high humidity, and great light. You can germinate in peat, sand, perlite, ground glass marbles, anything as long as the other conditions are good enough.

I think the absolutely most important part of starting seeds is to avoid chilling at all costs. Warm-enough "soil" temps are a must. Heat mats are often a good idea to try when you are having germination problems. Maybe try 75F / 25C to start. I put everything in a big fish tank just over a layer of water with an aquarium heater in it. Slam-dunk perfect temps (and perfect light too), but it's what I had laying around after the gerbils died.

For the most part (there are no absolutes here) don't fertilize seeds
that are sprouting. Sprouting and growing can be seen as separate
things entirely, and seeds can start out without extra food. I never
fertilize except when planting out into the garden or to a pot. It's what works for me. If you DO fertilize, do it
very weakly. Just a trace. As an experiment, try it on some of the seedlings and not others.

Finally, when you have problems that you can't get a handle on, be sure to sterilize your sprouting soil. Dampen it and nuke it. You may not have to, but it's good to eliminate potential fungus problems until things click into place.

There are seed which need chilling. And there are seed which need first warm and then cold.

I use commercial mix. What I do is use normal potting mix and spread a thin layer of seed raising mix on the top maybe 2 cm not more.

I do what loewenzhan does...my very porous potting medium as a first layer and a very shallow dusting of fine seed starting mix.

It's important to sow specific seeds in a manner with their needs....light/dark, depth, etc. My germination flats are always heated until the seeds have popped up after which I pull the plug of the heating cable.

I also fertilize when the plants are very young. I transplant the tiny seedlings into their individual cell packs and that's when they get their first dose.

Are your seeds dying before germinating or shortly after they've emerged? Makes a big difference as to the advice we can give.

I have been starting from seeds for 4 years now. The first few years I have been using straightly the seed starting mix from the stores with reasonable success given my set up of florescent lights and heating mats. Last year, I use a recipe that I read online with the same light and heat, etc. And I have very poor results. Germination rate was okay but my tomatoes (I have 2 trays of 72 cells each) were just not growing after the first couple of inches. I wind up buying seedlings from nursery for the year. I figure that the only thing different is the soil, hence the question. I want to get ahead of the next seed starting session. Thanks