Do your SEO yourself. That way you can be sure it is white hat. Plus, you'll save a tonne of money.

Just ask for the specifics on how they're SEO process works. For example, lots of the SEO providers here on WF include nice inforgraphics showing what they do, where links are coming from or generated, whether it goes through social networking sites, etc.

Anyone who won't tell you how they are doing SEO, is probably doing it blackhat... Unless they are really damn good at it and they are playing their cards close to the chest. In that case, you'd see tons of positive reviews pointing towards the legitimacy of said user or company.

Londonremovals,

Based on your question I would say that you wouldn’t know unless you did some research first. There are a lot of things that are clearly unethical and things that are clearly white hat however there are also tactics that fall into a grey area.

Without explaining the dozens and dozens of things that SEO’s can do, in general you want to watch out for SEO’s that are creating a poor user experience as a result of their work. As yourself, “would what they are doing be good for my audience” and if the answer is no then you may want to investigate further.

Ultimately though, if you don’t know a lot about SEO you won’t know the difference. It’s the same as knowing nothing about how your vehicle works and wanting to know if your mechanic is taking short cuts or ripping you off; you won’t be able to tell until negative consequences are apparent.

Here is a pretty good basic list of black hat tactics,

Black-Hat SEO Tactics Outlined by Beanstalk

Hope that helps,

Shawn

most of the time you can see it on the quantity of the links they do for you, for example:

Black Hat Company:
*2000 submissions, 1000 profiles, 500 comments, 50 web2.0 articles for 100$*

White Hat Company:
*10 high pr permanent comments dofollow, 10 web2.0 articles 130$*

As the first one seems more juicy, its completely blackhat automatized sh#t. senuke/xrumer etc.
Also first one the links will come from not only pr0 pages, but 95% of the forum profiles will even come from a pr0 root-domain, making them as useless as a fish in a wheelchair.
Also google will flag your website as spam very fast and you will get sandboxed soon or later.

hope this helps you