When you are sautéing meat or vegetables, make sure the skillet temperature is at least medium high, the oil is hot enough (you can just start to see wisps of smoke) or the butter has melted and most of the milk solids are gone before you add meat or vegetables. You can hear the butter sizzle and then it will stop, and that is when you should add the meat to ensure great even browning.
After you have added the meat or the vegetables, do not stir them until they have become the desired brownness you are looking for and then flip them to cook the other side. Do not crowd proteins in the pan if you want to brown them. Leave some space around them. Crowding creates steam and liquid and does not allow the protein to brown properly. Cook them in several batches.