I usually use an NPN Bipolar transistor to do the relay switching, mainly because my relays are 12v coil rated, but it also keeps everything nice and seperated.
A Solid state relay would be ideal for mains power applications, but can be expensive unless you can find a decently priced one!
Either way, as Bill said dont forget the clamp diode across the coil terminals!
The main thing I tend to see is people pushing the contact ratings to the limits and sometimes beyond!
Wilksey