Length and type of screws depend on the type of wall construction.
If the wall construction is cement, then use a TapCon brand cement screw, making sure the screw goes into the concrete a minimum of 1".
If the wall construction is wood studs and drywall we recommend Washer head or Wafer Head cabinet screws available at one of the home centers. The screw must go at least 1" into the wood stud (this dimension does not include any sheeting or drywall that may be over the studs, you must add extra length for sheeting). Keep in mind that there may be more than one layer of drywall on the wall, this is especially true for the wall between the garage and the house if the garage is attached. Code in many areas requires two layers of drywall to create a fire wall between the garage and the house. Several suppliers of these screws: