When it comes to deciding whether to plant seedlings or seeds, be brave and try seeds. You get much more choice and they are more affordable too. Start your vegie garden growing with large, easy to handle seeds, like beans, peas, zucchini or pumpkin.
Assuming your seed is viable, soil temperature is usually the main determining factor of whether a seed will germinate or not. Soil temperature can be accurately measured using a propagating thermometer but a meat or cooking thermometer works just as well. Push it into the ground about 10cm and leave it for 5 minutes before reading the gauge.
Generally, most seeds like a soil temperature around 23 degrees C, but some seeds have special requirements. Tomato, pumpkin, watermelon, rockmelon, zucchini, squash and cucumber germinate well within 20-26 degrees C, while broccoli, cauliflower, leafy greens, carrot, lettuce, beetroot and radish will germinate at cooler temperatures.
Sowing in pots or trays indoors is the easiest way to monitor soil temperature, but some seeds are best sown directly where they will be grown. These include root vegetables such as carrots, parsnips, beetroot, radishes and turnips. Seeds such as beans, corn, peas, zucchini, pumpkin, silverbeet and melons will also do better sown from seed directly where they will be grown, rather than transplanted as seedlings.
Plant about twice the depth of the seed, water in and keep moist. In current conditions with limited water available, a covering of weed mat or shade cloth will help protect the soil and seeds from drying out. Check regularly and remove the cover when the seeds begin to germinate.
Small seeds can be tricky simply because they are so tiny. Sometimes they get blasted out of the soil by water from the hose or watering can. Use a fine mist to water them or water from the bottom using a capillary type system.
Small seeds can also be buried too deeply, so try sieving a very fine layer of soil over the top of the seeds. Some fine seeds such as lettuce need light to germinate and so don't need covering at all.