Page 124 - 42 Rules for 24-Hour Success on LinkedIn: Practical ideas to help you quickly achieve your desired business success.

Non-Customized Email Signature – There is a
pretty simple and low tech way to get someone to
learn more about you and possibly connect with
you. Use a vanity link in your email signature. This
would look something like this
http://www.LinkedIn.com/in/JohnDoe. It shows up
in all emails and is a passive way to get people to
see all your credentials.
Groups – The jury is still out on the value of them
but, at the very least, you have the opportunity to
connect with people who have similar interests.
We've made some interesting connections this
way.
Answers – Ask and answer questions. It is a great
way to promote yourself. Generally expect to make
a couple of connections through each activity,
however we have heard about people that get 10
or more new connections through their Q&A.
Consider becoming a LION – A LION is a
LinkedIn Open Networker, meaning that you agree
to accept all invitations. The phrase is included in
your profile and thus searchable. People seek out
LIONs during searches to increase their network.
If quantity is what you are after, this is a relatively
simple and time effective way to generate connec-
tions.

108 42 Rules for 24-Hour Success on LinkedIn