First, a plea to any thrifty souls who carefully hoard elderly, half- used seed packs. Don't bother. Even the most resilient seeds lose their viability quite rapidly, especially if exposed to air, moisture or fluctuating temperatures. Seeds are relatively cheap, so buy only what you are likely to use in a couple of seasons. Throw out anything older than this, and treat yourself to a fresh packet.
Compost should also be fresh, as even stored in the bag it slowly deteriorates. Never be tempted to reuse old compost for seeds. It will be unpredictable in pH and fertiliser content and may well harbour diseases. Concern for peat resources has seen more and more peat-free mixtures appear in garden centres. I have used the same bark-based multi-purpose (I have never found a need for specific "seed" composts) for several years with excellent results. The only thing I regularly add to this mix is a top dressing of fine vermiculite, a naturally occurring mineral which is light and free-draining but also heat- and moisture-retentive, and thus provides ideal conditions for germination.
What to sow into? A standard seed tray measuring around 35cm by 20cm is useful for many things (such as chitting potatoes) but it is too large for sowing, unless you happen to have a field you need to fill with bedding plants. Far more practical is the quarter-tray, which is plenty big enough to germinate hundreds of smaller seeds or a decent number of much larger ones. I find the most versatile container of all is a simple 7.5cm plastic pot. Go for square rather than round, as they will pack more tightly together. Keen recyclers will no doubt conscript old yoghurt pots and the like, but, environmental issues notwithstanding, I would not recommend them. Purpose-made pots are carefully designed for optimum drainage and stability, and if you spend a little more on good thick plastic they will last for years.
There are lots of other options for sowing: compressed peat pots, expandable peat pellets, fibre grow-pots, home-made paper pots and so on. I don't bother with any of them, and suggest you don't either. All are biodegradable, the idea being to plant them out together with their contents. This, it is claimed, reduces root disturbance and helps the plant to grow away more quickly. My experience is that they can hinder root outgrowth after planting - and anyway, just how much root disturbance is there when a plant is tipped straight out of a plastic pot and planted?
I do, however, use modular trays. These have long been the norm in commercial horticulture and are now finding favour among home gardeners too. Basically they are plastic trays divided into a number of separate cells, rather like a honeycomb. Seeds are sown direct into each cell, either singly or severally (and later thinned). This means space for unfettered growth and no pricking out of overcrowded seedlings, which saves on both time and (genuinely) root disturbance. Either buy them as one-piece plug trays or as plastic inserts which are then dropped into a seed tray. The cells come in a range of sizes and though you should be guided by the size of seed, it is worth remembering that the smaller sizes hold a minute amount of compost, and to develop well the seedlings require careful feeding, watering and prompt planting out. Propapacks are a polystyrene variation on this theme, and I find them especially worthwhile early in the season as they give extra insulation to the young roots. Whatever you sow into, make sure you retain heat and moisture by keeping a cover on the seeds until they begin germinate.Reuse content