Try and work out what is causing the power to trip. Look at your fusebox: has the main (largest, and usually red) switch tripped (in the down position), or just one of of the smaller switches?
Turn off all the other switches (push them down). Now turn the main switch back on (by pushing it up). Slowly turn each of the smaller switches back on, waiting a few moments between each one. Try this a few times. If the power consistently trips off when you turn on a particular circuit, then the problem is likely to be with that circuit. Follow the steps below to find out what it is on that circuit which is causing the problem.
The switches should be labelled as “upstairs sockets”, “downstairs lighting”, etc. If the problem switch is labelled, then unplug (for socket circuits) or turn off (for lighting circuits) everything on that circuit. Turn the circuit switch back on at the fusebox and then slowly go around your house turning things back on on that circuit. Try this a few times. If something (a particular light, or a particular appliance) consistently causes the power to trip, then you’ve identified the likely source of the problem. If it is an appliance (like a toaster, for example), try using it in a different socket in a different part of the house. If that still causes the power to trip, it is possible that the appliance itself is faulty and should be replaced.
Even if this doesn’t help you solve the problem, it will be helpful for an electrician to know what you’ve already checked. Book one of our electricians online and let him or her know in the job description what you’ve already found out.