For some people, the best way to change a habit is with baby steps. They start incredibly small to avoid terror and procrastination and gradually work their way up from there.

But others are more the dive-right-into-the-cold-water type. For these folks, the best way to change your life is through a quick, sharp shock that promises both excitement and an instant peek at what a new lifestyle can offer.

If you're more the latter type, 30-day challenges might be for you. By pledging to make a big change to your life for just a month, you get around the paralyzing fear of failure and the unknown by setting a definite boundary for your project. You also fire up your competitive instincts and offer yourself a real preview of a possible new life that might tempt you to continue your project once the month has passed.

So what kind of changes are amenable to 30-day challenges? Tons of them. Here are some ideas culled from a variety of relevant threads on question-and-answer site Quora, as well as an excellent James Altucher post on the topic.

1. Negotiate once a day

"At a Starbucks? Ask for 10 percent off, for instance," suggests Altucher. Not only will this help you get over a fear that holds many people back and hone your negotiating skills, but you'll probably also learn that people are much more likely to agree to requests than you probably think.

2. Just say no

Don't want to do what someone is asking you to do? Then, for 30 days at least, just say no, suggests writer Nelson Wang on Quora. (Some essential requests--like those from your boss, probation officer, or wakeful newborn--are obviously excepted.)

A month of saying no will exercise your ability to set your own priorities and prove how much can be accomplished if you're ruthless about controlling your time. It will probably also reveal to the more tightly wound that the world won't stop turning if you put yourself first sometimes.

3. Quit social media

A heap of studies says you'll be happier without the likes of Facebook. So does Evopaper CMO Max Lukominskyi on Quora: "You will instantly notice how longer your day can be without it," he assures the leery. Come on, you can do it. Just imagine how much more you'll get done (or read).

4. Swear off complaining

Science shows this one could actually begin to rewire your brain for positivity. A bunch of different Quora respondents recommend this challenge, as does Altucher, though he warns it's easier said than done. He calls it "probably the hardest challenge" on his list, and notes that "whenever I try doing this I realize how often my thoughts settle on complaining thoughts."

5. Drink your greens

Looking for a more manageable, practical challenge idea? Wang suggests one in a separate Quora thread: Get your recommended fruit and veg with a daily green smoothie. "It can change your life," he enthuses. "You will feel healthier. You will feel sharper. You will feel empowered." Check out his complete answer if you want all sorts of details on his project and its effects.

6. Do standup comedy

This one isn't for the faint-hearted, but Altucher swears a weekly session of standup will change your life. "This breaks down every conception I've ever had about who I am, and what it's like to go in front of a bunch of strangers and make a total fool of myself," he says.

7. Talk to a stranger a day

If standup is too much for you, Quora respondent Mike Farkas offers a less extreme variation on the same theme. "Talk to one stranger every day. It doesn't have to be a long conversation. You can just start some small talk," he explains. Confronting fears is a great way to overcome them, after all, and this sort of "implosion" therapy has helped celebs like Conan O'Brien and Will Ferrell overcome shyness, according to reports.

8. Get up ridiculously early

Entrepreneur Skyler Irvine undertook this challenge involuntarily when his newborn started waking him at 4:30 a.m. each day, but then he embraced the change and started setting his alarm for 4. "The effect it had on the rest of my life was very powerful," he says, noting he quickly gave up his nighttime scotch habit. But that was far from the biggest change.

"I also saw my productivity shoot through the roof. Getting up at 4 a.m., feeding my daughter at 4:30 a.m., then having three hours to myself before the world woke up is incredible," he relates, recommending the challenge even to those who don't have a crying baby to tend to.

9. Take a cold shower

Turning the water ice cold for the last few seconds of your shower is another less-than-instantly-appealing idea from Altucher. It sounds crazy, but science suggests it really might make you more productive for the rest of the day.

10. Return an old email

Here's a less daunting suggestion from Altucher: "Return an email to someone from 10 years ago that you've never returned." (I'm sure five or two years ago is fine, too.) Not only will you reconnect with lost contacts and build your network, but "you'll be amazed how grateful and happy you make people," he says. Plus, making others smile is a great way to make yourself happier, too.

11. Write

Altucher has turned out 18 books with his daily writing habit, but this practice isn't only for would-be authors. Simply dumping your thoughts onto the page each day is a great way to boost your mental health and clear out space for creativity, according to experts.

Entrepreneur Ilyas Bakouch also endorses this challenge on Quora, calling it "great for memory, reflection, and especially awesome to look back to in the future."

12. Improve your push-up skills

If you're most interested in improving your physical health, then scientist Lukas Tencer suggests the 30-day push-up challenge. Simply start by doing the maximum number of push-ups you can as soon as you get out of bed in the morning. Then add one additional push-up each morning and evening until you're able to do 30 at a time (or whatever your target number of reps is). Not only will you be healthier with very little time commitment, you'll also get the satisfaction of seeing your fitness improve.

Have you ever done a 30-day challenge that changed your life?