How to handle email requests from people wanting you to exchange links with them
This one's pretty simple. In most cases you simply press the delete button.
Most of them aren't even from people, they are just robot generated and designed
to confirm that your email address has a sentient being on the end of it.
If you are interested in finding out more about them then the first thing to do
is look at the website it came from. If there's a link to it with a long string of letters and numbers
at the end (or even a relatively short one) then... hit the delete button.
Failing that, simply type in the website address in your web browser (this is probably
a better idea than clicking on the link).
I use the same criteria as that described below for deciding if I want to pursue the
relationship further.
How to establish mutually beneficial relationships with other sites
The whole idea of getting links to and from your site is, really, to provide
your customers with quality. This should be the highest priority when looking for sites to
link to. "Does this link provide my viewer with something of value?"
You need to be discerning.
Again, Harry's letters are a good example. In the process of looking
for subject specific sites to link to, I came across sites that had the same kind
of feel to them as mine.
Firstly I put a link from my site to theirs. I did this
because I thought my visitors might be interested in the site. I found a
page in their site, where I thought a link to a page of mine might be useful.
I sent a polite email telling them that I was researching
(describing a little bit about my site) and that I had come across their site
and liked it (the truth, in other words!).
I advised them that
I had linked to them and I thought they may find page xyz interesting and if
they'd like to link to me I'd be grateful (or words to that effect).
End of story really. If they link back or not does not really matter.
My motivation for adding the link still holds (useful to my visitors) and if I get
a return link so much the better.
Simple idea but,
firstly it takes time to find the sites;
it needs good email & writing skills (the two skills are not the same),
and it takes time to write the emails; and
if you're in business this implies that you'll be getting links from your competitors
(in theory at least). You may want to consider businesses on the other side of town,
or in another state. Businesses up and down the supply chain are also often good
candidates. | 
a sensible way to provide your visitors with high quality cross references and distractions;