The steps for encounter and combat are as follows.
1. Determine if either or both parties are SURPRISED.
2. Determine distance, if unknown, between the parties.
3. If both parties are unsurprised, or equally surprised, determine INITIATIVE for that round.
4. Determine the results of whatever actions are decided upon by the party with initiative:
A. Avoid engagement (flee, slam door, use magic to escape, etc.) if possible.
B. Attempt to parley.
C. Await action by other party.
D. Discharge missiles or magical device attacks or cast spells or turn undead.
E. Close to striking range, or charge.
F. Set weapons against possible opponent charge.
G. Strike blows with weapons, to kill or subdue.
H. Grapple or hold
5. Determine the results of whatever actions are decided upon by the party which lost the initiative (as per A. through H. above).
6. Continue each melee round by determination of distance, initiative, and action until melee ends due to fleeing, inability to continue, or death of one or both parties.
1 Turn = 10 Rounds (each 1 minute)
1 Round = 10 Segments
1 Segment = 6 seconds
The activity of player characters and player character-directed creatures must be stated precisely and without delay at the start of each melee round or before the appropriate divisions of other situations where exact activity must be known.
If you are a stickler, you may require all participants to write their actions on paper. Conversation regarding such activities is the same as if player characters were talking aloud, of course.
Delay in deciding what is to be done should be noted, as such hesitation will basically mean that the individual is not doing anything whatsoever during the period, but he or she is simply standing by and dithering, trying to arrive at a decision as to what should be done.
Combat is divided into 1 minute period melee rounds, or simply rounds, in order to have reasonably manageable combat. "Manageable" applies both to the actions of the combatants and to the actual refereeing of such melees. It would be no great task to devise an elaborate set of rules for highly complex individual combats with rounds of but a few seconds length. It is not in the best interests of an adventure game, however, to delve too deeply into cut and thrust, parry and riposte. The location of a hit or wound, the sort of damage done, sprains, breaks, and dislocations are not the stuff of heroic fantasy. The reasons for this are manifold.
As has been detailed, hit points are not actually a measure of physical damage, by and large, as far as characters (and some other creatures as well) are concerned. Therefore, the location of hits and the type of damage caused are not germane to them. While this is not true with respect to most monsters, it is neither necessary nor particularly useful. Lest some purist immediately object, consider the many charts and tables necessary to handle this sort of detail, and then think about how area effect spells would work. In like manner, consider all of the nasty things which face adventurers as the rules stand. Are crippling disabilities and yet more ways to meet instant death desirable in an open-ended, episodic game where participants seek to identify with lovingly detailed and developed player-character personae? Not likely! Certain death is as undesirable as a give-away campaign. Combat is a common pursuit in the vast majority of adventures, and the participants in the campaign deserve a chance to exercise intelligent choice during such confrontations. As hit points dwindle they can opt to break off the encounter and attempt to flee.
With complex combat systems which stress so-called realism and feature hit location, special damage, and so on, either this option is severely limited or the rules are highly slanted towards favoring the player characters at the expense of their opponents. (Such rules as double damage and critical hits must cut both ways — in which case the life expectancy of player characters will be shortened considerably — or the monsters are being grossly misrepresented and unfairly treated by the system. I am certain you can think of many other such rules.)
One-minute rounds are devised to offer the maximum of choice with a minimum of complication. This allows the DM and the players the best of both worlds. The system assumes much activity during the course of each round. Envision, if you will, a fencing, boxing, or karate match. During the course of one minute of such competition there are numerous attacks which are unsuccessful, feints, maneuvering, and so forth. During a one-minute melee round many attacks are made, but some are mere feints, while some are blocked or parried. One, or possibly several, have the chance to actually score damage. For such chances, the dice are rolled, and if the "to hit" number is equalled or exceeded, the attack was successful, but otherwise it too was avoided, blocked, parried, or whatever.
Damage scored to characters or certain monsters is actually not substantially physical — a mere nick or scratch until the last handful of hit points are considered — it is a matter of wearing away the endurance, the luck, the magical protections. With respect to most monsters such damage is, in fact, more physically substantial, although as with adjustments in armor class rating for speed and agility, there are also similar additions in hit points. So while a round of combat is not a continuous series of attacks, it is neither just a single blow and counter-blow affair. The opponents spar and move, seeking the opportunity to engage when an opening in the enemy's guard presents itself.
Because of the relatively long period of time represented by the round, Dexterity (dexterity, agility, speed, quickness) is represented by a more favorable armor class rating rather than as a factor in which opponent strikes the first blow. Likewise, weapon length and relative speed factors are not usually a consideration. (See Initiative and Charging, however.) The system of AD&D combat maximizes the sense of hand-to-hand combat and the life-and-death character of melee without undue complication. Because of this, you, the DM, are enabled to conduct such portions of a game without endless resort to charts, tables, procedure clarifications, and over-lengthy time requirements. Players, on the other hand, will not become bored with endless dice rolling and rules consulting, but at the same time will have a reasonable chance to seek escape for their characters should the affair go badly.