Take a look at a seed catalogue, most will have some sort of notation about a seed's germination requirements, or you'll pick up a few clue-in phrases.

Look for these terms:

Reseeds or reseeding

Wildflower

Will Colonize

Self Sows

Hardy Seeds

Can be direct sown early

Seedlings can withstand frost

Sow outdoors in early Autumn

Sow outdoors in late Autumn or early Winter

Sow outdoors in early Spring while nights are still cool

Sow outdoors in early Spring while frosts may still occur

Weed (such as butterfly weed, joe pye weed, jewel weed)

Needs Pre-chilling (freeze seeds, refrigerate seeds, stratify for x amount of day or weeks)

Needs Stratification