I personally use Autosmart Tardis but if its something you want to get pretty soon the Autoglym Tar remover is good, just spray on leave for 20-30seconds then wipe off with a clean microfibre cloth

Clay will remove tar but its better to use tar remover
As for clay i mostly use Sonus Green if i am not polishing the car as it is not very aggressive as anything more agressive will leave marring to the paint that will need machine polishing to remove.

Hope this helps