Lent is a period of spiritual preparation for Easter, which involves penance for the sake of our own purification.
The three standard pieces are prayer, fasting, and almsgiving. Prayer: conversation with God. Fasting: giving stuff up. Almsgiving: giving to the poor.
I find it best to pick something from each of those three categories. I also recommend making those things small, concrete, and doable.
In other words, don’t be so unrealistic with your expectations that you set yourself up for failure. It might sound good to say that every day you are going to suddenly go to daily Mass, go to an hour of Eucharistic Adoration, pray a rosary (all 20 decades), pray a Divine Mercy chaplet, pray the Liturgy of the Hours, give up candy, give up coffee, give up snacking between meals, give up TV, give up the internet, give up your smart phone, sell all you have and give to the poor, etc., etc. All those things might be good, but it’s not likely that we will follow through on all of them simultaneously if we’re not accustomed to doing any of them (nor would it necessarily be good for us to do so). Then what happens is we get discouraged when we find that we’re not doing it all, and then we abandon the whole lot of it.
We also want to avoid being vague. Saying “I’m going to pray more” is too vague and we will end up not doing anything. Instead say, “I will set my alarm 15 minutes earlier so that I can begin each day reading from the Gospel of Matthew” (for example).
As (name removed by moderator) said, we are only obligated to fast on Ash Wednesday and Good Friday and to abstain from meat on those two days and all other Lenten Fridays. So we don’t have to “give something up.” But I highly recommend doing something else. Making a deliberate choice to do something extra (or give up something we like) out of love for God is a good way to draw closer to God and grow in holiness.