Pretty simple for us - some flowers, diner and some hot sex.

We don't do much usually, just have some nice dinner or something

Something simple dinner home cooked and doing something we both enjoy and sex if it happens it happens XD

We take turns each year, one of us surprising the other with evening plans. It's been everything from the classic romantic dinners at home and elaborate bedroom scenarios to a trip to the jousting show, the massage spa, or various other places.
Eventually we plan to renew our vows in a Pagan ceremony since our first one was somewhat traditional for this day and age. Maybe for our 30th anniversary.

Usually a nice dinner out, but I will sometimes surprise her with a nice piece of jewelry too on special anniversaries.

Some sort of gift, a good meal, time together, and sex. Pretty standard.

Except for when our anniversary fell during the week that Humans versus Zombies was being played on our college campus - that made for a long and silly evening full of Nerf guns.

We're sorta long distance so every year we switch off on who visits and we celebrate for the weekend, going to dinners, giving presents, just spending quality time together