Good quality ones !

Seriously though, buy a decent brand. Far too many people buy really cheap 'ditchfinder' (usually unheard of chinese tyre makes), and are then surprised when their roadholding, cornering and comfort levels go to hell. If the tyres that have been on from new were good, and have lasted well, then go for the same again.

There are plenty of tyre fitters - both independent and chains. In addition, there are a few online companies, some of whom will come to your work or home to fit the tyres for you. Use all of them for pricing, and as a negotiating tool.

Buy once, buy quality, buy right.