Think of it this way. I can
limp 66 in the CO and continue if I hit a
set on the
flop, or I can
raise 66 in the CO and c-bet regardless of if I hit a
set. First way gives me one way to win (and only 1/8 times), second way gives me two ways to win and if I cbet 75% of the time I do that 6/8 times. Also when I hit my
set its more hidden, whereas a limper (or
limp/caller) who suddenly gets all aggressive is more transparent.
Likewise with pretty much any cards you play PF. Limping will generally only give you one way to win (at least until you get good at postflop poker) whereas raising gives you multiple ways WITH ANY HAND!
Also consider this. Lets say you're playing 10nl. If you
limp the
button and SB completes, you have a 0.30 pot. If they both
check flop and you
bluff bet you win .30. However if you
raise to 0.35 on the
button, the SB folds but the BB calls, you now have a 0.75 pot. Most villains
fold to c-bets around 80% of the time, so 4 out of 5 times you c-bet 0.50 you win 0.75 ($3.0) and lose 0.5 once, for $2.50 profit. Thats $5 per 10 times you
raise PF and c-bet. That completely disregards the times you actually hit something big when the BB doesnt
fold and you play for a bigger pot. At 10nl, thats some pretty nice free money.
So as Hawkfan said, its less about aiming for specific
stats, and more just generally its better poker to
raise most hands you intend to play. My general feeling though, is that if theres more than 5 difference between the two, its probably not very optimal. So if you're playing 20% of the hands, you should be raising at least 15% of them.