Airmiles is the granddaddy of all the loyalty schemes and is currently making a comeback. The best way to use this scheme is to shop as normal on the high street. Then go away and compare prices and specifications. If you still like the item you may then reserve it through the airmiles site so that it is there for you when you come back. This counts as a Internet purchase which entitles you to airmiles that will be credited to your account.
It is generally better not to spend your miles on flights. This is because the likes of Ryanair sell flights so cheaply that this is no longer worthwhile. I would order a mixed crate of wine (at 650 miles) which is actually very good.