Here's my standard guideline, updated since I've learned a few tricks in my old age:

<a href="http://www.mudcat.org">Click here</a>

<a href="mailto:joe@mudcat.org">Click to e-mail</a>

If you're posting links at Mudcat, the quotation marks are optional. I prefer not to use them, because they complicate the task of making links. Simple is better, I think. Fewer misteaks.

I find it's best to open a new browser window [CTRL-N] and navigate your way to the site you want to link to. Highlight and copy [CTRL-C] the URL (address) of the site, and then go back to your Mudcat message and paste [CTRL-V] the URL into your link. Be sure to include the http:// in that URL. The quotation marks are standard procedure, but most links work just fine without quotation marks.
-Joe Offer-