Multiple attacks
The 'multiple attacks' skill is a passive skill that is always in use. It can be best learned by warriors and thieves, and is usually acquired gradually.
The multiple attacks skill increases the number of average attacks you make per round. In addition to training to get higher attacks, there are also certain pieces of equipment that can boost your number of attacks.
Unlike other skills, you may only practice multiple attacks as your level increases. Your thief and warrior levels have the biggest impact, and you should check to see if you can practice multiple attacks after leveling.
Higher attacks are good, as it will give you a much higher rate of attacking during combat.
Note that 'multiple attacks' is the only remaining truly hardcoded skill. It has no skill entry or position in the global skills table, and as a result it cannot be improved through use or via any other mechanism other than the 'practice' command.