I have a site that I want up and running as quick as possible. The main keyword may get me in the sandbox. Would targeting a not so popular keyword work and then switch over to the main keyword after a few months ?
choose a long tail keyword for now with most competitive main keywords in it, build on it and then later move on to main keyword. U gonna be boxed anywayz, dont fear it, embrace it and go all out blasting back links from good websites.
Of course start off with some less competitive search terms as that would be useful in getting your site seen at a few places and hopefully generate some income.... but as a strategy to avoid the sandbox i don't think its particularly effective. Prepare to be sandboxed anyways.