Quick Question - Raise First In?

[Twitch1977]

I have heard it alluded to a few times on the board but I just want to verify it's correctness:

If I am the first person entering a pot am I usually best off raising? And if so what sort of hands would I *not* want to raise with?

Thus far I have been following SSH's recommendations of when to raise different positions, but maybe I should be abandoning that and just shoving the cash in if I'm first in?

Thanks
T