I have basic Shimano mechanicals and they are pretty simple to maintain.
Guard against contamination of the disc. If you do get oil on it, dont apply the brakes. I find it best to remove the disc, scrub in detergent and water to get all the crud off then finish with solvent (methanol).
Pick your pads with care, there are some really good 3rd part pads that are a fraction of the price of the brand name items. You need to bed in new pads: braking hard to generate lots of heat to smear pad material on the disc. I start on a big hill and brake hard without skidding.