Some seeds need light to germinate so you normally scatter the seeds on top of the soil then a light covering of sand or grit etc. When they germinate and have put on some growth I normally pot on as I would any seedling.

Lupins do not like their roots broken as I have found out via transferring self seeders (gravel and spaces between patio slabs seem a favourite!), so be careful in planting those seedlings up.

I tend to grow all my seeds in seed trays with cells and then just plant the whole thing, sometimes if they get a bit leggy I carefully add a little compost around the seedling but try not to get it too wet

many seeds have the ability to drag themselves down to the right depth as do bulbs etc.

Thanks for all your comments. Much appreciated, and thanks for your time.
Mark