Are the windscreen wipers working properly? Do the blades have a nice firm edge and clear all the water from the screen?
Do the windscreen washer jets spray the screen evenly over the wiped area? On most car's the aim can be adjusted using a safety pin, but if you have a blockage, you may need to consult your local garage.
Check your windscreen for chips and cracks. Your car can fail if there are any within the main field of vision (swept area of the screen). If in doubt, ask your local garage before submitting the car for MOT.
Check that the engine oil; and coolant levels are correct.
Visually inspect the tyre tread and pressure. Remember to check the sides of the tyres too. Is there any obvious damage there such as cuts or bulges? If in doubt, ask the garage to take a look before taking your car in for an MOT.
Do all the seatbelts work properly? Are there any cuts in the belts?
Test that the boot, bonnet and doors open and shut correctly.
Check that all exterior lights work well. (Front fog lights and reverse lights are not part of the MOT test).