How should we observe Lent? Catholics are often eager to share what works for us, and eager to warn others away from what turned out to be disastrous for us. But, as Jimmy Akin points out

The traditional custom of giving up something for Lent is voluntary. Consequently, if you give something up, you set the parameters. 

Not only do we set the parameters for what we give up (sugar in coffee? A second cup of coffee?  All the coffee?), but we decide what kind of thing we want to give up (or take on) -- and why. Here are a few broad categories of ways to observe the penitential season. One or the other may be more spiritually fruitful for you, but none of them is really wrong.

 

Lent as marathon.
You choose some challenging practice that you don't intend to keep up indefinitely.
Examples: Following the drastic fasts of the Eastern Church; going to Mass every day throughout Lent; completing a course or set of spiritual exercises or retreat which has a definitive end point.
The benefit: Your penance or practice really shakes you up, sets Lent apart from ordinary time, and gives you the opportunity to show God that you're serious about changing.
The pitfall: Unless you have a particular kind of personality, taking on too much means you're likely to crash and burn, and then waste the rest of your Lent feeling like a loser. You also run the risk of turning Easter morning into a bacchanalia as you rediscover the pleasures you gave up. Taylor Marshall has a funny cautionary tale of what happened when he found himself suddenly able to eat meat, sugar, and booze again. again. 

Lent as reset button.
You choose some practice that you hope to continue after Lent is over.
Example: Limiting how much time you spend on your phone; incorporating spiritual reading or regular prayer into your daily routine; purging less-healthy foods from our diets.
The benefit: It's an achievable way to become a better person with better habits, which is basically our job here on earth. 
The pitfall: You may secretly be trying to achieve some kind of self-improvement which isn't all that spiritual -- like losing enough weight to fit into your smokin' hot Easter dress; or, as soon is Lent is over, you may immediately slip back into your bad old ways. 

Lent as an opportunity to give up something you shouldn't be doing anyway. 
Example: No yelling at the kids or insulting strangers in traffic; no overeating; no watching movies you shouldn't be watching
The benefit: You humbly avail yourself of the special graces of the season to become more holy.
The pitfall: It may be hard to know how to feel when Lent is over. Jennifer Fulwiler explains why she gave up sugar in her tea along with giving up cursing one Lent

I pictured myself rising on Easter morn, taking a deep breath, and shouting the f-word. Umm, yeah. That’s why giving up something that’s bad anyway doesn’t quite have the same effect. So no sugar in my tea for Lent.

Lent as an opportunity to sacrifice something pleasant or nice
The benefit: As I tell my kids, God doesn't need anything from us, so if we want to give Him something, one way we can do this is to give up something good that we have. And of course there is a long tradition of showing your body who's boss, of clearing out the everyday clutter of life that prevents us from encountering God, and of showing God sorrow for our sins and gratitude for His salvation.
 The pitfall: You might find yourself checking your God Duty off the list, as if it's just one more chore. Regular sacrifices can give us constant reminders of what we are supposed to be doing, but they can also become a substitute for what we're supposed to be doing. If God is calling you to repair your marriage, going forty days without Snickers bars is probably not going to help. 

Lent as a way of focusing more on other people
Examples: Saying "yes" to other people as often as we can; giving extra money, time, or attention to people who need it; performing acts of service beyond what we normally do
The benefits: "Whatsoever you do for the least of my brothers, that you do unto me."
The pitfalls: Focusing on other people can be a great way of avoiding a mirror. 

Lent as a way of focusing more on your own life
Examples: Saying a rosary in the car instead of listening to music; sleeping without a pillow. 
The benefits: It's a great time to narrow in on one virtue you want to cultivate, or one flaw you want to root out.
The pitfalls: It's hard to see your way to heaven when you're navel gazing. It's not all about you; it's about Christ, and it's about Christ in His "distressing disguises." 

Lent as a way of making a space for God in your life. 
Examples: Just about anything could go here. 
The benefits: All the benefits! Whatever the specifics, the overarching goal is to grow in Holiness, and to become closer to God. Because there are so many different kinds of people, there are many different ways of doing this. What is cumbersome or useless for one person might be a life-changer for someone else, and what is helpful one year might bomb the next. That's why Lent comes around every year. 
The pitfalls: Making a super plan, but forgetting to let God in on it. There is no Lenten practice that will bring you closer to God unless you ask God to help it happen. If you get someone a present, you have to put the right name on the tag, or it's wasted effort.

And what about practices which are nothing but pitfalls? Oh, yes, there are those, too:

Lent as a way of torturing everyone you know and love
Example: giving up coffee cold turkey. Just about everyone I know has tried this at one point, and their families have invariably begged them to start drinking coffee again. Unless you're a hermit, your decision will affect other people. The rule of thumb is that you get to choose your suffering. Not everyone else's.