rough guide...
<9 months, rear facing baby seat
>9 month < 3 years, forward facing 5 point harness
>3 years, Booster seat,pref with adjustable back to hold seatbelt
>4 years Booster seat, poss with strap to hold seatbelt
>12, Normal seatbelt.
very rough off top of my head. Ages very approx, its all on height really
Good post HOWEVER.......its a bit more complicated than that.
My two were very small for there age and we were told that its very important for a child to be able to sit up unaided for approx 30 seconds (due to strength in neck muscles) and be over a certain size as you say

...One of my twins now has a forward facing seat and the other is no where near ready despite being the same age.
Basicly if the comfortably fit in a rear facing car seat thats without question the safest option...failing that a forward facing just make sure who ever has bought it has looked at saftey and comfort as opposed too style.
Could cheerfully slapped the woman next too me in Kiddicare who said ""Na i dont like that it looks crap....i like that one it looks better"" despite it being blindingly obvious it had NO padding and Looked like it was straight out of a rally car.
Simple cow didnt give a toss about the kid"s comfort just how it would look in her MG 25 thingy....

Just read back....oh 3 yrs old.....ignore the above
