Mostly I decide what to do for Lent by praying about it beforehand.
To me, it is important that the primary goal of whatever I give up is sacrifice. So for example, it may be good for my health to give up all eating after 8pm. In the context of a diet, it wouldn’t matter if I had sugar-free mints or sugar-free jello or diet soda or something. But in the context of sacrifice, it would lessen the sacrifice if I made it easier on myself by low-cal snacks. So if I give up eating after 8pm (a bit of a hardship as I almost never go to bed before midnight), then that means NOTHING passes my lips except water from 8pm until whenever I get up in the morning. Hunger reminds me to pray, and that Jesus didn’t eat from the arrest through the crucifixion.
Or when I gave up meat, I also gave up “fake meat” like the textured-vegetable-protein “chicken” nuggets (which are pretty good, BTW), and also things that have unexpected meat products in them, like the broccoli-cheese soup made with chicken broth. I reminded myself to pray when I was scrutinizing the labels of unknown soups.
I always say a daily rosary in Lent. You’d think that it would by now have caught on to the rest of the year, but not yet. Also there are other intentions that I include in my daily prayers in Lent which I pray about less often (e.g. weekly) outside Lent.
In our diocese (at least) there is a collection for the Holy Land on Good Friday. I usually save up money throughout Lent and put it in this collection.
There are some other things I do as well. Some years it’s more than others. One year, I allowed myself $20 a week for food (I live alone) including all eating out, etc. That helped with the whole “solidarity with the poor” thing (and incidentally reminded me of some periods in my own past!). But as adults it should be a re-ordering of your life (to some extent anyway), not just the “giving up chocolate” that we all did at some point when we were children.
One thing about the Catholic practice is that Sundays during Lent are NOT part of Lent. Sundays throughout the year (even in Lent) are days on which we rejoice in Jesus’ resurrection. And if you count it out, it is 40 days between Ash Wednesday and Easter Sunday only if you do not count the Sundays in between. So although you should of course still engage in the extra prayer parts of your Lenten practice, it is entirely up to you if you choose to do the fasting part on Sundays. In some ways, not performing the fasting on Sundays makes the rest of the week harder (which is partly the point!), so sometimes I do, and sometimes I don’t, continue the fasting on Sundays.
Best wishes,
–Jen