House Critic

In a busy market they will not be interested in you if you are dithering about, or are not sure what you actually want.
First make a list of everything you want from your house.
Budget, number of rooms, parking, garage, garden size. Every item you add will help you work out what you're looking for.
This is important to give you an idea of what you are actually after. Sit down and compare lists with the person you are buying a house with. Do you have the same list of requirements?
Draw an area on rightmove and set up alerts to get the new properties emailed to you. You can set many of these up if you are looking at a couple of areas.
Sometimes you can register with all the local estate agents - you can actually do it via rightmove. Despite the internet being a strong search place you can still call in at most estate agent offices and speak to someone who might pull a property out that you hadn't considered.
They will want a clear budget from you - but feel free to look at houses that have been on the market for a long time over your budget. There is always a deal to be done, and if not then it's why the house isn't selling. You might get in at the right moment that someone is fed up of not having an offer at the price they want.
If you view and don't like a property then try to work out what was wrong with it - if the kitchen was too small then the estate agent will know not to show you more like that unless extention work has been done.
Generally all houses on the same street will have identical layouts. Unless any have had extensions or alterations that is.
Estate agents can only show you what they've got on their lists. And some will push what they've got that isn't selling.

If there's an EA not using rightmove check their site and speak to them about being emailed about possibles.

But research research research.

Keep notes on what goes for sale in your preferred area and what is selling. Know the market. Ring and ask about anything above your price bracket that's been on a while.

Does propertysnake.co.uk still work? That can point out long unsold ones.
By viewing stuff that's almost right you'll start to work out what's important. View different style houses to the ones you think you want. A victoria house might just be the thing you want rather than a modern new build. Try to view as many properties as you can. Don't be frightened of being the first viewer in when a house comes on the market though.

Someone's made some changes to estate agent signs in London - see this story at the metro paper