Agree fully with your appraisal of LinkedIn as superior in functionality and ROI to Facebook and Twitter Donna. I am Founder/Admin of LinkedIN's top ranked parenting group, Parenting 2.0, and the quality of connections I have been able to make in a very brief time is nothing short of phenomenal.
New users get stumped precisely where you did - connecting with others - so much applaud you perservering and figuring out that groups provide the secret key to unlocking LinkedIn's gold. Since people can join up to 50 groups - which I recommend everyone doing (you can adjust settings to minimize emails) there is plenty of room for variety. Once members join a group they can extend network connect requests to fellow group members without knowing members' personal email.
One important tip I would add to your five is to always personalize your connect requests and whenever possible include a compliment - especially if you are writing the Admin :) Hugs!