I have a site in a competitive niche which I have carefully built over several years, being very conservative with content and careful with SEO techniques. I have made reasonable and steady progress in this niche which I do not want to jeopardise.
I am considering launching a second, totally unrelated site and plan to be a bit more experimental with the content and the SEO (but nothing black hat). However, I am worried that "bad experiments" with my second site might harm the Google rankings for my first site. Is there anything I should or shouldn't to in order to avoid this?
For example:- Can I host both of the sites on one account (eg as an add-on domain)? Can I track both sites using my analytics account? Can both domain names be purchased with the same domain name registration account? Anything else?
The basic question is can one penalized site hurt other sites that are seen to be related to the same owner. The answer is sometimes yes.
You say you will not be doing anything "black hat" but there is no technical definition for black hat - it's just a kind of slang term. So it all depends on how "experimental" or high-risk you intend to get. If you raise a flag and get a manual inspection for something that really pushes the guidelines on a new domain, then I think your clearly related domains might also get a manual inspection - a real "white glove" look over, you know?
Running into an over-optimization penalty that gets levied by algorithm is not likely to spill over to your other domains - but pushing too hard on the guidelines just might.
If you are aiming to be experimental, then why not make the two sites completely different in every way, including hosting separately, using a different tracker, different registration account etc as well as a different site structure -sometimes by doing things differently you can learn a lot.