If you have already decided which river to fish then you should go to that river's section (choose 'Areas & Rivers' in the salmon fishing menu above) and refer to its pages on where and when to fish. These should help you choose a suitable beat and a particular time of year.
Remember that whatever your decide, you may be constrained by price and/or availability. For example, there is no point choosing the best week of the season on the best river, if there are no rods available or the price is beyond your budget. You will often be far better fishing a good beat at off peak times or take 'shoulder' weeks around peak times.
Before booking, the first thing you should decide is how flexible you are on the dates you fish and the notice you need of these dates. If you are flexible on both, then you can follow the conditions, catches, prospects and availability pages in the relevant river secction and book at the last minute when you see everything looking favourable. Undoubtedly this gets you the best value for money fishing and can sometimes reveal a last-minute bargain when other tenants can't manage their pre-arranged dates and have to relet in a hurry.
If you are not able to be flexible on dates, because of prior commitments or are part of a larger group, then you will need to book well in advance and hope that the conditions suit you when the time comes. Remember to read the relevant pages for your chosen river, since this is only a guide to help you decide which river to fish, if you haven't done so already. Another important consideration is what type of fishing you require.
These may be the most famous rivers, however, larger beats can pose a problem for those anglers not used to casting long lines with large rods, or fishing from boats with the constant presence of a ghillie. However, if this isn't an issue, and you have a pocket to match, then they will offer the best chances of a fish when booked a long time ahead. The ghillie's advice and encouragement can also be on a par with some of the best professional instructors. The Tay and the Tweed are the largest rivers on this site yet some of the Lower Dee beats are similar.
Smaller rivers will suit independent and experienced fishermen since ghillies are less often supplied than on the larger rivers. Those who dislike fishing with large rods should also consider this option, as should people who like fishing in the uplands. The upper beats of the Dee are beautiful and full of Highland character and it is a smaller river than the Tay and Tweed. The Esks are smaller rivers still and well suited to independent fishermen.
Loch fishing for salmon is less easy to find in Scotland but there are some fine examples of small loch systems with interconnecting rivers in the Western Isles, many of which are quite famous, prolific fisheries.
If you want to fish for sea trout then consider the Esks and some of the smaller rivers on the West Coast. In addition some of the larger rivers have a good sea trout run - the Tweed in particular often produces some large specimens. Its tributary the Till is a well known sea trout river, as is the Earn, a tributary of the Tay.