Following the puzzlement on how I made the loop on my throwing knife instructable, I thought i'd make one on the things that can be done with hot steel. I've missed a few out because i think the basics are covered here. If you want to make a bar thinner, for example, you only need to use a slight variant on Drawing out the bar. If you try this a bit, you'll get the hang of it.
The only thing you have to know is that you're changing the profile of the bar, but leaving the volume the same. You can beat it out into foil, or forge it into a sphere, but it'll still be the same volume.
Step 1: Upsetting Steel bars
Not upsetting as in "Making Steel bars Unhappy", but reducing the length of the bar and making its cross-section larger.
Heat the end of the bar, or the bit you want to be wider to forging heat. Place the bar end-down on the anvil and hit the top, like hammering in a nail. If it cools down too much, put it back in the fire until it gets hot again, then carry on. Upset the bar until it's at the desired thickness.
You can use Upsetting to put bulges into a bar, or to make rivets, nails, bolts, ETC