How do people stay so steady when painting such small figures and such?

Practice, practice, practice

I like to do all my detailing painting when everyone's in bed sleeping. No one comming into the room, no phone, just nothing but pure quiet.

Both Jesper' and Joe's points are valid.
I also find that having the right tools helps. I use really fine, good quality brushes. I also have a headset with a light and various magnifying lenses.

All 3 of these are what it takes in my mind. The skills involved will come with practice, but peace to paint in and with a decent brush and properly thinned paint helps as well.
I have become very interested in painting figures, and over the last year or so, I have seen a huge improvement in my work. It all comes down to the above three, plus listening and reading good advise. Post you pictures on here and get the advise needed. That is one of the best tips I recommend. Another thing, dont compare your work to somebody who has been painting for 20 years. You have to learn first. I read a lot of articles in magazines and on the net. Then I would get a figure and try to copy the steps ... step by step ... from these articles. I didnt suceed on a lot of occasions, but I learnt a lot. All this experience has helped. Good luck. Figure painting is a very rewarding part of the hobby and bring any model scene alive.

One of the deep dark secrets is to get yourself a nice firm foam pad, to rest you hand/forearm on as you paint.... helps steady the holding hand, and cuts down on fatigue. I found the thicker the better, as long as your forearm and hand are comfortable. Also I adjust the chair height, so I don't need to bend over as much.

Shhhhhishhhhhh don't tell everyone........ :-) :-) :-) :-) :-)

practice and patience, practice and patience......and a good brush

I have to echo all the sentiments here mate !
if figures are your thing or just the ability to paint tiny details accuratley i use kolinsky sable brushes ,from winsor and newton's series7 miniature brushes these will take a lot of abuse although theyre around £6.00 each ,but theyll last almost forever i buy a new set every 2 years!
i also have learned to use my little finger as a pawl stick
resting it on the figure or model to act as a pinion joint to give me free range but steady strokes! all practice and quality materials mate !

I use paper towels