I found this on the internet and have out it here for your information. It gives the main things that you need to know and do. It is extracted from the Highways Agency website.

Fit To Tow?

Keep your trailer ready to go.

If you’re taking to the roads with a caravan, trailer or horsebox, don’t set out without a final safety and maintenance check, especially if you leave it standing for most of the year.

Before setting out, make sure your trailer is properly serviced and fit to be on the road. Your trailer should be given a regular service by a reputable dealer.

Fit to Tow Video

To raise awareness of the safety risks involved when towing a caravan or trailer and the importance of ensuring you are towing safely, the Highways Agency has issued a new safety DVD, Fit to Tow, presented by Carol Smillie.

Please select the video file below. Different video file formats will be made available shortly along with a full text transcript of the production. If your PC does not have the necessary plug-in you should be prompted to install it.

High quality MPEG View (48MB)

Here is a simple checklist for you to download and print off: Fit to Tow Checklist (84KB PDF)

Before you set off:

Carry out a final maintenance check before you set off.
Is the load correctly distributed and firmly secured?
Are all the lights undamaged and working correctly?
Are the tyre pressures correct and all tyres in good condition?
Is the trailer correctly coupled to the tow ball or pin?
Is the coupling height correct? It should be level.

On the Road

Driving with a loaded trailer will inevitably affect the vehicle’s performance:
Moving off needs more effort.
It will take longer to slow down and stop.
You need to take extra care when negotiating sharp bends.

You need to check:

That the vehicle and trailer are loaded securely and correctly distributed in accordance with the manufacturers' specifications.
Are you adequately covered for recovery and breakdown?
Most recovery agents won’t cover a trailer unless it’s specified in your contract. Make sure you have specialist breakdown cover. Standard trailer insurance does not automatically include breakdown cover.

Reversing with a Trailer

Make sure the area behind you is clear before reversing.
Be especially aware of children and pedestrians.
Try to get somebody to observe for you.
Practice makes perfect! Try reversing before setting off.

Have you got the Right Licence?

An ordinary category B licence allows you to drive a vehicle up to 3.5 tonnes Maximum Gross Weight and to tow a trailer that weighs up to 750 kilograms Maximum Gross Weight, giving a Maximum Combination Weight of up to 4250 kilograms.
Drivers who have got a B category licence are entitled to tow a trailer over 750 kilograms Maximum Gross Weight provided that the gross weight of the trailer does not exceed the unladen or kerb weight of the towing vehicle, and the maximum combination weight does not exceed a total of 3.5 tonnes.
If you want to drive a larger vehicle or pull a heavier trailer you will need to take a category B + E driving test.
For more information visit: www.direct.gov.uk/en/Motoring/DriverLicensing

Speed Restrictions

Always keep within the legal speed limit.
30mph limit applies on all roads with street lighting unless signs show otherwise.
50mph applies on single carriageways unless signs show otherwise.
60mph applies on dual carriageways and motorways.
NOTE: You must not travel in the right-hand lane of a motorway with three lanes or more.
Avoid problems before they happen

Following these 4 simple rules could help you to avoid unnecessary repairs.
Avoid parking your trailer on long grass - moisture could damage it.
When you park up, you must not leave a detached trailer on a public road. If it is hitched up it must always be parked with lights on at night on any public road.
On a level surface if it is safe to do so, avoid parking with the handbrake on.
Grease all the greasing points with a grease gun, plus the brake cables or rods, and handbrake.

What if you break down on a motorway?

Remember it is illegal to stop on a hard shoulder except in an emergency.

If an emergency forces you to stop, then follow these top 5 personal safety tips from the Highways Agency:
Pull onto the hard shoulder and park as far to the left as you can.
Turn on your vehicle’s hazard warning lights.
Leave the vehicle via the doors furthest away from traffic and stand as far away from traffic as is safe.
Contact the Highways Agency using the emergency roadside telephone.
Follow the instructions from Highways Agency staff.