Look on Ticketmaster. They sell returns 48hrs before for the show courts.
They also have some reserved seats that are only sold the day before for centre and usually #1 Although this year looks like its #3, maybe due to the new roof/refurb.
Have look on Ticketmaster, and be ready for the sale, they go in seconds. Be logged in and on the page ready for the timer to get to zero for the sale to start and try to get in basket as soon as on sale. You then have a few mins to checkout. Dont fanny about with options just leave it as 2 tickets and best available. if you spend time changing anything you will miss them.
Max 2 people and the cardholder must collect on the day with card and photo ID.
I have managed to get tickets this way every year for a day or two. I am not going this year as I have used all my holidays on euro aways.
The seats reserved in centre court are the back few rows, but it's still a good spec to watch it from, I think they are a bit cheaper too. Returns can be anywhere, and different price ranges. We have had some great specs from the returns.