I use the inSim mod to summon the members I want to the home. For example, in my game I have two (cas family) teens I wanted to have kinda of been aquaintances/grown up together. I used the summoner to bring her to the lot on the day they moved in then let them chat so that she would be in his friends list to call.
I only use it for the first meeting because when you summon a sim it's not a natural game occurance but the relationship will be; so say if you summon her to his house and save your game went you come back to your game the previously summoned sim will not be at the house still (but the friendship will still be in his list).
You can also use inSim to simply make all the people on a lot friends or even friend the entire neighborhood with a click or two...but I don't use the second option because (when I did before) it even friended the repo man

and the social bunny, & who wants the nutty bunny as a bff

?
Ok ok even social bunnies may need love but not from my sims

.
A reminder if you use the inSimenator:
1- it goes in your downloads folder
2- only use one version of it
3- understand that it is not supported by this website--Don't ask if it will be upgraded, etc as it will not.
I dont think the tutorials on it's use made it to these threads. but there are a few on here: http://www.sims2wiki.info/wiki.php?title=InSimenator
4- that said I use the mod in my game I will help you if you have a question or two.
Oh and also creator Christianlov (MTS2) has an "easyphone" mod:
http://www.modthesims2.com/download.php?t=293793You can use this to invite a sim over who doesn't have a phone; also has an easy call feature that will open a neighborhood phonebook to invite any unknown sim to your lot (and they'll all say "sure! be right over!" )