There are a number of factors you need to consider;
Budget - Are you buying new, nearly new or used? Given your lack of mechanical skill, most new or nearly new cars can include both a warranty and servicing package.
Use - What do you use to car for? If it's typically just you driving or you and one other you won't need as large a vehicle as if you have a family. Also, if you use your car for work, a large luggage area may be useful. My brother is a musician and has a car where the seats can be removed effectively turning it into a van.
Condition - If you are buying a pre-owned car, irrespective of age, you need to assess the mechanical condition. Knowing that you know very little it may be worth taking a mechanic with you or a "car person". There are motoring organisations which offer professional inspection services for a fee which, unless you are buying a 10 year old plus car, would be worth considering.
Maintenance - When viewing a car you need to know about it's maintenance costs and service schedule. Whilst a brand new car may go a year or two before it requires any significant time in a workshop, an older car may need maintenance work right away. Look at how often a car is supposed to be serviced and look at when it was last serviced. Most cars have a handy book which shows mileages and has a space for a mechanic to stamp or sign to say work has been done. If a used car doesn't have any stamps in its book and comes without any receipts for any parts, you want to consider the cost of a full service and get the price reduced by at least this amount.
Fuel type - certain cars make a great noise and accelerate quickly but use a lot of fuel. Others might be slow but you can go a longer distance between fill ups. Typically for longer drives, a diesel will give better economy than a petrol but if you only do relatively short journeys (just a couple of miles) then a petrol may make more sense as diesels can silt up their emissions control kit if they don't get taken on longer journeys which can be expensive to repair.
Regulatory Inspection - in the UK we have a test known as an MOT where a qualified mechanic must warrant that the car is still safe to use on the road. Most countries have such a system with cars being inspected every year or two. If the car you are looking at hasn't been inspected in a while, either get the seller to have it inspected or budget for some expense when this falls due. A car which doesn't have any current road worthy certification should be avoided unless you know what you're doing mechanically.
Colour / Trim / Model - If the aesthetics of the car are important to you, you pay a premium for this. I am a "car guy" and my current car is black. I could have had the same car is gold with beige seats for about three quarters of the price I paid but the look of the car was important to me. If you aren't bothered by this you can save a fortune in buying a well maintained but unfashionable car but bear in mind that such a car will be harder to sell when the time comes. The model / trim / specification may also be important. You might find a car which is the type you like but doesn't have features such as air-con or cruise control. Again, only you can answer if these things are important to you.
Hidden costs - alongside fuel and servicing costs, you need to take into account how expensive the tyres are to replace, how much the insurance costs, how much road tax or registration costs will be.
Finally, when you've decided on a car you like, Google; read reviews, join the owners club forum and ask what the common faults are, watch independent road tests from when it was launched to help you confirm if you've made the right choice.
The only other piece of advice I can give is to listen to your gut. If you're looking at a car, the numbers all look good, you like the car but there is a voice inside your head telling you something is not right - walk away and find something else.
