This is the age of penances and fasting. I have a few simple suggestions.
One, if you are praying for a person who is an alcoholic and has fallen away from the Church, give up beer.
Two, if you are praying for someone who is ill and has fallen away from the Church, give up desserts.
Three, if you are praying for someone who has depression and has fallen away from the Church, give up complaining and judgemental attitudes towards others.
Four, if you are praying for someone who is addicted to computer games, give up movies or television.
Five, if you are praying for someone who is contracepting, give up shopping for unnecessary items.
Our prayers, as Jesus Christ indicated, are more efficacious if coupled with fasting. Fasting may mean cutting back on food or it may mean giving up other pleasures.
Penances for others also help us on our way to perfection. God will not be outdone in generosity and doing penances consists of acting out of charity and generosity of heart.
I am sure you can think of more.