1. Putting it on

Your corset is made to your measurements and will fit you perfectly (if you haven't lost or put on much weight), but you still have to be careful when putting it on and lacing in to avoid being uncomfortable or even damaging your health. Above all - I'm talking to beginners now, the experienced already know this - have patience! You can't put the corset on for the first time, lace down from 65 cm waist to 50 and stay like that, smiling, for 12 hours. Make the experience a pleasant one, so you'll want to repeat it. Lace the corset snug and wear it for an hour or two at home; do it again tomorrow, the day after tomorrow and so on, whenever you please. Gradually you can lace tighter, but take very small steps. Fully boned steel corset will press at your ribs and the excitement may make it bearable, but in the evening you will find two nice bruises on your sides. That's why you need the patience ;) Let your body be used to the corset and the corset to your body and you'll both be happy.

Before you put your corset on, put on everything that will go under it (meaning both under and from the waist down) - underwear, stockings or socks, skirt, lace-up boots. 19th century ladies did it like that and they knew why - you cannot bend in a corset. (Don't even try that - by bending forcibly you could damage the bones.) If you have a maid, you can omit this warning.

If you have a corset with busk, lace it before you put it on, undo the busk, put the corset on, fasten the busk and then tighten the laces. You can do it alone or you can ask the maid. Tell her to pull loop after loop from top to bottom; always pull on both sides and steadily, without tugging or jerking. The corset may look like the sturdiest thing in the world, but such manhandling may damage it. A corset without busk can also be laced prior to putting it on, but you will need a longer lace and lace it more loosely, so you can pull the corset over your head. During lacing in keep checking if the corset sits comfortably, if the waist is not too low or too high or the whole corset askew. Wriggle a bit, move the corset with your hands, adjust the décolletage, after tightening the laces it won't be possible anymore.

2. Lacing in

There are basically two ways to lace a corset: "the shoe" or "the cross". Both can be done with or without a loop at the waist.

the cross

The loops allow maximum tightening at the waist. Lace the corset from top to bottom and leave a loop at the waist - see pictures. Tie the lace at the bottom, then pull at the loops and tie the loops at the waist. The two pairs of eyelets at the waist are closer to each other - this is the place to make the loops. If you don't want loops, just keep lacing.

the cross with a loop at the waist
left: simple loops
right: double crossed loops. Use when the eyelets are too spaced.

You can also use two laces and lace one from top to waist, the second from bottom to waist, then tie everything at the waist. But the loop is less complicated.
Don't tie the loop around your waist! It's a bad habit that will damage the fabric and bones at the waist.

the shoe with a loop at the waist

the cross, ready to make the loops at the waist