I am trying to implement a standard footer that I can include/add to various email templates - is there a best practice to go about this?
Pls move this to Products (Move link at the right -- this isn't a support space, it's the webmaster feedback spot).
In you email template, create a mktoSnippet element (or a mktotext element). Then create this footer as snippet and you are done. Easy to spread and reuse, easy to create a couple of version to address specific cases, easy to protect from unauthorized changes through roles and easy to update when time comes.
Christine Rios Snippets are also great if you use Marketo segmentation because you can have regional specific footers within the same snippet. (ex. Address footer: if lead is in North America, show the North America HQ address. If lead is in EMEA, show EMEA HQ).