Perhaps unrivalled in the garden for their floral effect in spring time. Admittedly the flowering season is short but the fragrance and size of blooms more than makes up for it. All Lilacs prefer a sunny site and well drained soil, preferably on chalky soil, but they will tolerate most sites unless your soild is particularly acidic. Prune after flowering, removing the dead flowerheads and also 50% of last year's growth - this encourages dense bushy growth and better flowering the following year.
The most familiar lilacs are the vulgaris types, commonly known as French Lilacs. They are some of showiest of all, with large dense panicles of sweetly scented flowers in a range of whites, pinks and purples. These are also the most vigorous, and can get to 4-5m on maturity (although regular pruning after flowering can keep them much smaller).
Some of the less well known hybrids such as S. meyeri 'Palabin' and S. x josiflexa 'Bellicent' are definitely worth considering - the flowers may not be quite as showy, but the fragrance is out of this world.