I’m getting started on a project and the client has multiple domains that covers alternate spellings. It’s a bbq site so it has barbeque / barbecue / bbq versions of their domain (as well as .ca and .com versions). Is there anything I should be doing (SEO-wise) other than forwarding the alternate domains to the main one?
Forwarding is the right approach. Alternatively, putting the same content in n each site would have negative consequences. There would be duplicate content, and the sites would complete with each other.
The other domains could be created as satellite sites, feeding back to your main site. I’ve done this loads of times, with lots of success over many many years, just make sure the content is written in different ways, different H1s etc. Use region specific alt tags and image file names,
Use these sites to aim at different regions around you, so if there’s a town 5 miles away, make the SEO specific to that town / area . These smaller domains actually work for you, rather than just forwarding to the site ( forwarders have no set value ) . It does depend on your hosting package , but if you have a reseller account its virtually free. Even better if you have a friend with hosting capabilities pop them on there, mixes up the server addresses.
When I had the bigger sign business about 14 years ago - I did this and filled up all 10 slots on Googles first page for van lettering for our county. I used to do it to upset the competition :) If you need some help with this get JW SEO Helper stacks, they are invaluable.