Take the vehicle to an authorized service center. Request for a general check up where leakage's and damages would be repaired. Also worn parts would be identified and replaced. Special attention would be paid to Hoses, pipes & cables. ( clutch & accelerator specially) Fuel lines should be paid extra attention. Ensure all fluid levels are as recommended by the manufacturer. Ensure the brakes are looked at and any defects are attended to. Ensure all lights are checked and are in satisfactory working condition. Also check the vehicle horn for satisfactory operation.
Make sure you give the vehicle for a check up well before you plan to travel, as if left till the last moment you may be delayed or the job may be slip shod due to the urgency.

Ensure that the tyres are in good condition and would stand the rigors of your trip. It would be a good idea to have one extra tube placed in your vehicle to avoid over charging and waste of time by road side Tyre repairers. Ensure the stephney Tyre is inflated to the recommended pressure. Please note that if the vehicle were to be fully loaded the Tyre pressures would be kept slightly higher.

Reduce tyre pressure by about 2-3 psi on high-speed roads as the Mumbai-Pune Expressway or the Delhi-Noida Expressway. High vehicle speeds on these rpads for long distances results in heating and automatic inflation of the tyres. If the tyres are already over-inflated, the hazard of a tyre burst is omnipresent.

Ensure that the vehicle body jack is available and is in a working condition. At times the jack spindle catches rust due to long periods of non-use and the jack would be difficult to operate. (If a situation like this emerges lubricate the spindle to get the same moving freely) Ensure that the jack handle is available in the vehicle.
The wheel spanner would need to be in its place and secured like the jack and handle, if unsecured it will rattle and make irritating noises.
Carry a set of open-end spanners, reversible screwdriver, a pair of pliers, torch. For spare carry a set of drive belts, hose pipes, electrical wire piece, insulation tape, extra fuses, and coolant.
Always carry a first aid kit to meet any unfortunate eventualities. Try to keep the kit as comprehensive as possible.
You may not know how to repair the vehicle but if the tools and spares were available with you it would be easier for a roadside mechanic or a good Samaritan to help you repair the vehicle so as you are not stranded on the highway.
In case you feel that you need professional help get in touch with the Highway users club.

It makes a lot of sense to carry the Service Manual of your vehicle on long distance drives. The manual always lists the closest available authorised service station for your car if the need so arises.

Always pre plan the route you intend to take (eg. Use a state or highway map of India) prior to actually commencing the trip. WIAA is amongst others organizations that would be in a position to help you layout a route that would be both convenient and safe. You will be supprised at the different possibilities that would be available. Also you would be in a position to make note of refueling stations, service centers and rest areas.
Also your family would be aware of the route taken by you and in case of an unfortunate incident of a brake down they would be in a position to help.