If you have any suspenders you'd like to wear even though they're very old, (I mean, those you'd normally need buttons for), here's how to make them work without sewing buttons on every pair of pants you own.
In addition, the result may be a bit crude, but it definitely can be used with steampunk outfits.

Supplies:
old suspenders
3x suspender clips (what we normally see on suspenders nowadays)

Step 1: Start With One End

For a clearer idea of what I mean, also see photos
* Take one end and one clip
* Pull both leather tails through the loop of the clip
* Twist the tails
* Thread the clip itself through buttonholes so that it's held in place by the leather and, at the same time, it also locks the leather loops together
* Pull to tighten, you should end up with something like the last picture

Step 2: Repeat

Just repeat as needed. In this case, 2 more times...

Step 3: It's Ready to Wear!

This may be more bulky than modern suspenders or old suspenders used with buttons the way they were intended to, but it's functional - so if you need to keep your pants from falling, without using belts nor sewing, grab your grandpa's suspenders, clips and give this a try.