Check if the forums allow signatures and if you can put your website link as a signature.

Most forums allow you put your website link on your profile too. Also, your website might address a need on the forum, simply post your website links in appropriate places, I hope you find this useful.

There are actually a lot of various strategies you can use on forums - it depends upon your goals.

If you're wanting to focus more on link building (and at this point, I'm not really sure that you want to - I've done some testing on forum links, and we're not seeing any boosts at all), then consider developing a persona that is not related to the business. Register he/she on the forum, get in there and genuinely participate in conversations for a spell, then CAREFULLY insert a link to a product page or piece of content on your site when the time is right. If forum links that pass juice do work, then it's probably best to link on a thread that pre-exists but is neither brand new or inactive.

If you decide to register as an ambassador of your store, there are sometimes opportunities to have a signature link (I haven't seen any SEO advantages from them in the last 3 months). Otherwise, I recommend trying to engage and help people on the forums each day with your expertise to further brand yourself and your store. This will give you referral traffic and reputation, and if you're into content contributing, you will likely run into site owners there in your niche that will get to know you, and your reputation could help generate guest posting opportunities.

Setup multiple accounts, one for you, a few for your "friends".

When you bring something up, make sure your friends vouch for it.

Or your friends post up links to your site when it becomes relevant on the forum.

Then you've got a squad helping you promote it, without being labeled as a "self promoter".

Don't spam though, homie. Provide legit help and nobody will know it's you.

You can't control how other people advertise your site. Or just happen to bring it up in conversations on forums where you also happen to hang out.

Get my drift?

It's not popular, but it works. Manipulating traffic (cheating), and spamming are two different things, Kay!

Spam is what we have on the WF when people attempt the strategy.

You can't tell it's being done when it's being done properly. That's what I meant by not spamming.

Timing. The best thing you can is to just go with the flow.
If you can't talk about your product then just be active and engage in the community.
You'll not just increase your brand presence but also your reputation.

All the input has been really helpful. I guess this all goes along the same lines as what I've read about how to get traffic from reddit; be a part of the community and VERY occasionally drop a link to your site when applicable.