Starting tomatoes from seed indoors

[astrbac]

Hello!

I am a beginner gardener and have a few questions, so if anyone would help out I'd appreciate it :-).

I am starting some plants from seeds, indoors (from March):

- tomatoes
- Tall Utah celery
- radishes
- basil
- parsley
- rosemary
- ricola (? Italian lettuce, kind of, with jagged edges)

Now, my practice is as follows:

1. I put the seeds in a paper napkin, wet it a little, place into a plastic bag
2. i keep it warm and moist for a few days
3. when the seeds start sprouting I sow them into the small jiffy boxes (peat containers)
4. for the next few days/weeks I keep them near the window and/or on a closed western oriented balcony
5. I rotate them once a day if they bend towards the light
6. I water when the soil gets dry from the top (?)

My biggest issues are temperature and watering - how to know when there isn't enough water and when it's too much, and also, when to take the plants outside?

I keep them in the kitchen during the night (temp 18 deg C; closed balcony about 10 deg C). Somewhere around noon I take them outside on that balcony (14 deg C). When the sun hits it, it shines directly on the plants, and it gets to about 20-ish deg C. Again, when the night falls, I take them back inside.

Wrong or right? They all seem sturdy and fine except for the 3 or 4 tomatoes that simply withered and fell flat on the soil.

Cheers all!
Alex