How to stop spaghetti sticking?

[MummyPenguin]

My DH and DC's love a good spag bol but as soon as I serve up the spaghetti (the normal type boiled in the normal way with a little salt added to the water.) The bloody stuff sticks together as if glued. I prefer the wholemeal kind myself and it doesn't stick like the 'normal' type. DC's and DH don't like wholemeal though. So, how to stop it sticking? I know you can buy those Knorr cubes that you add to the water (do keep meaning to get some) but are they any good? Any other tips for a stick-free lovely bowl of spaghetti?

On another note, when I was younger and DM wanted to get us all eating wholemeal, she started my mixing white and wholemeal, so 20% wholemeal for a while, then 50/50 until we were all happy eating all wholemeal. It does taste a little different if you aren't used to it, but you might find this a good way to wean them onto it.