Artificial cover objects (AC or ACO) are good for many species. Corrugated iron or roofing felt (easier to carry and less likely to be stolen). Diferent species have different preferences for size or material. I'd recommend Bird and Peak (2009) "A snake hunting guide II" as a good primer for catching snakes in N. America and I enjoyed the humour too. Lift the AC using either glove or a butcher's hook / stevedor's hook.
It depends largely on the species. Check papers herpetological journals for their exact methods. Grabbing by hand, tongs or snake grabbers, and so on. Definitely need to know venomous from non-venomous species.
Corrugated iron mats are preferable over roofing when catching snakes, the latter being used predominately for lizards. The attached document highlights some useful information in regards to the best time to look for reptiles, although conditions are likely to vary to those in the UK.