Oil. It is the very blood of the motor. If there were little or too much, you could have a 'heart attack' gripaje as having no lubrication between moving engine parts. If you had to add the plug is usually yellow, have yellow letters, include the word OIL or drawing of an oil.
Refrigerant. Complements the work of lubricant lowering engine temperature. It is in a transparent plastic container with a black plastic plug. If you have to check your level hot, watch out !. Grab the cap with a cloth for protection from splashes and open it slowly.
Windscreen. A blue plug, water color, often identify the washer fluid. It is less worrying if your level is low, but do not overdo add water.
Brake fluid. Even if you are going to probably never have to add. Either way, the level must also be between the minimum and maximum. A generally black cap with an emblem of a disc and circular paths around the lines identified.
Steering fluid. The most modern, with electric assist addresses cars lack hydraulic circuit, nor have cars without power steering veterans.
Battery. In some cars it is not found in the engine compartment but in the trunk. There are no maintenance, but in others it is good to check your level and sometimes having to add distilled water. It is recognized by having an elongated plastic sheet under which are holes or separate plugs.