After the purchase
The first thing to be done after the purchase is the service with a competent mechanic, regardless of whether you bought a new or a secondhand bike. The sellers often pack bicycles in such a way that its parts are held together until the sale day, so one should not put faith in "I bought a new bike, why would I need a mechanic". Fine adjustments of its parts, oiling and adjusting the bike to yourself precisely are prerequisites for enjoying the ride. Later on interventions will be significantly easier if the basis is covered thoroughly.
The bike cleaning
Keeping the bicycle cleaned is the important element which should come as a routine of every biker, because in that way one lessens fraying its parts and keeps mechanisms functional and reliable. In order to keep the hygiene of the bicycle on high level, it is enough to own the equipment which can be found at any center and whose price is not high. This involves different brushes (for the ram and wheel washing, as well as washing of some inaccessible parts), cotton cloths (for drying and polishing), degreasers (which can serve as oil degreasers or petrol, but special degreasers are more eco-friendly), cleaning agents such as sponge and water. The device for chain cleaning is a desirable piece of equipment, but not necessary. Sprockets, chain and exchaning parts are greased parts which should be washed with a degreaser in order to take off the old oil, grease and deposited motes. The soap which is used to wash the bike is better if used in hot water, and one should pay attention not to direct the water or soap jet towards the bearing. This is especially applicable for the devices for pressure washing. Rinsing with clean water and drying are the next phase and compressor water exhausting can accelerate the drying. Then the part oiling follows (scarce oil, WD-40 etc, depending on what is to be oiled), as well as removing the extra lubricant (with cooton cloth).
The equipment which should be carried
Even relatively short rides imply wearing some equipment: Spare inner tube, pump, and the most basic tools, while helmet, gloves and suitable clothes is obligatory. One can never forsee every single situation which can happen while riding, so there will be some cases in which the aforementioned equipment will not be enough, but at least one shold have the most basic one. However, carrying more equipment will be more difficult. Water, food, the lights, documents, GPS device, a phone... This list could be continued but the final choice depends on the cycler's needs.
The terrain which mountain bikes are made for are demanding, and it is important that their construction is solid and durable and the key part which holds everything together is the ram. Nowadays, the rams are made of different materials, mostly from aluminum-based and carbon-based alloy but from other materials as well, such as: titanium, different types of steel and combinations of aforementioned materials. The manufacturers tend to lessen the difficulty and strengthen the rams so they use different approaches in material choice and geometry design. Geometry differs a lot from the one used on road bikes, and there are even significant differences among mountain bikes, depending on the terrain and the discipline they are intended for.
The choice of tires used in mountain biking is huge, and they differ based on their dimensions (mostly from 26 to 29 inches, according to the diameter point), the "balloon size" (mostly from 1.95 to 2.30 inches), type of hinge (wire, Kevlar etc), the design of tread surface (crampons of different density, depth and design, as well as silk tires) the direction of fibler interference which are used as a basis for tire layer, hardness, composition etc.. The case is similar for inner tubes which are different according to their composition, wall thickness, valve type (car valve, Schraeder, Presta) as well as dimensions (according to diameter point and the size of the "baloon").

Zlatibor 2010