One very important thing you must know when searching for tickets online is that it will be displayed a face value and a selling price of the tickets. The face value of a ticket is the price that the producers set for the ticket. Most of the time the ticket agency will purchase the ticket from the theatre at the face value. They then must clearly state this price but also they must show the selling price, which is what you will pay. The difference in the face value and the selling price is the booking fee you are paying to the agency per ticket. The agencies can add anything up to 25% of the face value of a ticket as their booking fee.
This isn't always the case however, as the selling price can sometimes be less than the face value if the ticket agency have a special deal going on with the theatre. This won't usually be for every performance of the week but can be for all Monday to Thursday shows and can often be a considerable saving as the theatres want to get as many people coming to their shows, even in the more quiet weekday shows. The weekends generally aren't discounted as this is the most busy time and prices for top price seats for one of the more popular shows can go back up to £70-£90 per seat.
If you are searching online through the various ticket agency's websites then make sure you don't buy the first seats you find. As the ticket agency's are all allocated a different section of tickets, it might not be until the last website you are on that you find seats closer to the front or more central for the same price you saw on the first website you visited. It's always best to be patient and look around and it will pay off.
One last thing to be extra careful about is to make sure you are on a legitimate ticket agency's website. There are definitely places online which aren't legitimate and will take your money, never to be heard from or seen again. One way to do this is to look for the logo for S.T.A.R on their website. S.T.A.R is the leading self-regulatory body for the entertainment ticket industry across the United Kingdom. The abbreviation stands for the Society of Ticket Agents and Retailers and when purchasing tickets through a STAR members website you can be sure that the face value and any extra booking fees will be clearly stated, you will receive a refund if the event is cancelled and all terms and conditions regarding transfers, cancellations and viewing restrictions will be clearly displayed before you make the final purchase.
Whether you are looking for a musical like Chicago or a play like The Woman In Black, there are a few key things to remember. If you are patient enough to look around for the best seats at the best price, and make sure you know the face value and what you have paid for the ticket, then you are bound to find the best theatre tickets London can offer you at the lowest possible price.