Regular bird feeders for seeds can be bought or made out of milk cartons, pop bottles, juice jugs…just hang and wait for birds (just make sure there's no sharp edges). A good tip if you are making them is to make sure you put a few drainage holes in the bottom for water or they fill up if it rains (we discovered this the hard way unfortunately). It’s also important to remember that seeds can become mouldy and poisonous if they are wet, so change them often. They are also hard for the birds to get if they are frozen in a solid chunk of ice (yep, hard way again). You can also just fling some seed out on top of the snow on a nice day and see who shows up. The best all-purpose seed is black oil sunflower seeds (not the stripey ones) as it's a favourite of a lot of birds.
A handy-dandy chart of who eats what!
The one thing they do have trouble finding in the winter is water - so next up is a non-frozen bird bath, and maybe a suet plug feeder, and a birdhouse.... Dear Santa....
Some good pages on bird feeding for those who want to know more: