A lot depends on where you are. If you are in CA you can probably put them right into the ground. Where I'm at, it's really not warm enough to put autos (which can stunt if exposed to cold weather) out until the beginning of the second week in June. "Warm enough" for me means daily highs in at least the mid-to-low 70's and overnight lows above 50º. Cool weather, including cool nights and mornings, can really slow them down and I've had a few strains that never really recovered from a cold start.
It varies a bit from season to season, but I always start them indoors in 1 gallon pots. I tend to start them the last week in May (unless they are known to be 11-12 week strains, in which case I'll start them earlier), and then if it's a mild spring I might put them out after only two weeks, in the first week of June. If we're having a longer colder spring, I'll hold them back in their pots another week.
I'm planting into an established garden with several year old raised beds, so I'll add about a half bag of fresh FFOF around each new transplant, and then just augment the soil similarly to the way I did when I grew photos outdoors, just cut back on the amounts. I used dry time release nutes. So far I've found that autos outdoors can be grown much closer to way I used to grow photos outdoors, than their indoor equivalents. What you will do will depend on the condition and type of soil you have natively, and what your goals are for plant size. The better the soil, the better the plant.
I'm not an expert, that's just what works for me. You have to look at the overall length of your season and determine your goals. For instance, my primary objective is to be finished before the end of August if possible, and no later than mid-September when the rains come -- so I plan backwards from there. Finishing in August is nice, the days are longer, the sun is still fairly high, and the nights are not so cool that everything is wet with dew in the mornings. Get into September here, and everything changes quickly and gets sketchy.