Some of the indispensable bedding flowers are best sown now, such as Lobelia, useful for stuffing in here and there. The seeds are tiny to the point of invisibility, so make up your seed tray and sieve an extra-fine layer on top of the compost.
Then, mix the seed up with silver sand and tap the lot steadily across the compost surface: if the sand is evenly spread, the seeds will come up evenly spaced. Water them by standing the tray in an inch of water until the compost surface glistens. No further watering will be necessary until after the seedlings appear.