What to do if the .com domain for your idea is taken?

I vote for D since trying to buy domain name from owner could be expensive and not worth going for it

Add something to the unavailable domain is my preference D, but what ever you add, don't make it too long, try to keep it around 8 chars max

Option C worked well for us. There is no harm in trying.

    A) Get a top-level domain such as .net or .info?
    B) Get a country code level domain such as .us or .cc?

.org is better - there's wikipedia, craigslist, wordpress, thepiratebay, all in top 100.

If you look at alexa top sites, there's not a single .net or .info site in the top 100.

First .net site: secureserver.net (106th place)

First .info site: com-net.info (807th place)

First .us site: imageshack.us (132th place)

First .cc site: wretch.cc (287th place)

    C) Lookup the information of the current owner and try to buy it from them

Assuming you can find them and they answer the email filled in their whois.

    D) Keep the same name but add something to the end of it, 
    e.g. "burgersapp.com" instead of "burgers.com" (if it's an 
    app for burgers)

No.

    E) Think of a different name for your product

That's definitely one of the best ways, if rebranding is not an issue. Notice that most of the top websites have completely made up names that don't say much about the business - google, youtube, yahoo, linkedin, amazon.

    F) Something else (please explain)

Check out domain auctions, you might find something short and sweet for a reasonable price.

  D) ...
  No

whats the space? think of an alternate name.

Is the .com you like doing the same thing as you?

F) Go to Google Translate, type in variations of your desired domain in English, then try out most of the languages until you get a short, pronounceable, memorable word or phrase, then register thatphrase.com.

English: hack me, hackme.com, not available.

Danish: hack mig, hackmig.com, available.

Icelandic: hakk mig, hakkmig.com, available.

Indonesian: hack saya, hacksaya.com, available.

Norwegian: hack meg, hackmeg.com, available.

Swedish: hacka mig, hackamig.com, available.

Bonus: you get to make up some cool, interesting back story.

spell it differently

Definitely try to buy it. A good domain is well worth it.

Probably though it'll be too expensive (unless you have significant funding).

Keep it mind that it's extremely easy to convince yourself that a particular domain is The One. It really truly never is. It's really hard, but you can find another one that's good (often better).

F) http://domai.nr

your name being 4 letters makes that less useful than it would be otherwise.

So D) is probably your best bet for the reason pavpanchekha and Joakal already suggested: if you're successful you can buy the original domain name you wanted like dropbox, mint, facebook, twitter, etc.

Maybe try getting the same 4 letters twice in a row if that works...

C.

We were in the same situation and settled for mispelledword.net while we were in dev - until we stumbled onto an auction for the word.com and picked it up for ~$2k. We were incredibly lucky though.

If you can't reach them or don't have the budget and that name is The One go with D.

I'd go with option D - if your app takes off, you'll be making enough money to buy the "proper" domain. That, or use a random word generator to create a brand name. Protip: if you go down this road, do a Google first just in case it means something unexpected :)

How do you mean, "if"?

There are lots of successful apps with great names and less-than-ideal URLs - 37 Signals seem to be doing just fine with BasecampHQ.com, HighriseHQ.com, CampfireNow.com and BackpackIt.com. I use BeanstalkApp.com and PostmarkApp.com.