How can I best help my fiance with his online store?

Set him up on twitter and tweet sales for him as well as interesting news on electronics.
Have him review new products with his honest opinion on sites like Amazon.
Have him blog about items. (you can have the blog posts auto-feed into the twitter too)

Those are just a few free ways that may help. I am sure there will be more coming,.

google ad sense

If you have the time and are a decent writer with some basic research skills, then writing content, TITLE tags and META description tags for product and section pages and such can be a great help. Often the store owner is just far too busy to take the time to do these things. Stores end up using boiler-plate content and head tags borrowed from the manufacturers of the products they offer.

The problem with this is that the major search engines recognize duplicate content. Using the cut-and-paste approach ensures that whoever used that particular content first (in the search spider’s eyes) gets the credit for it and all the :me too” sites get none.

Past that, you can blog about what his store is up to, or participate in discussions about it on social networking sites. Just review the site’s spam policies first and be sure to always err on the side of caution, as people will often yell “spam” even when you are well within the site’s terms of service.

Set up a facebook site for his site and encourage your friends and family members to become ‘fans’ of it. It’ll help get the name out there that way. Facebook also offers advertising, which my sister says works really well (she owns her own online business as well). As @JONESGH suggested, Google Ad Sense is super, as are blogs.
And of course be supportive! It may not help with sales, but sometimes a little mental support makes a world of difference.

poster ask your friends every one you and you fiance know.. btw GOOD LUCK :)

You might want to mention the endeavor in your profile here, and post a link to the site after explaining what you are doing for it. I don’t think Fluther would see that as spam. Unreciprocated links from high Page Rank sites are geart for Search Engine Optimization. Just be sure the main keywords for his site appear in the anchor text of the link. Same goes for a Facebook page or pages on any other Social Networking sites.