Running White Plume Mountain, I ran into the issue of the rather complex AD&D initiative system.
I'd downloaded documents like the ADDICT PDF and a by-the-book flowchart for initiative. It's complex. I didn't need complex. It has features that aren't always helpful but can be decisive in very specific situations (weapon length, weapon speed factors.) It has stuff spread all over a number of pages.
I wanted a pretty simple system, but one that didn't depend on arbitrary rules ("Missile Fire Phase" or "No Spells after Melee Begins" or such as that). I also really do like segments as a concept. My favorite initiative system for Rolemaster assigned points to activities and you'd use them to line up who did what, when. Ironically that system didn't go far enough - it had the basis of an overlapping phased system that would like like an overall-round-free version of Champions 1st edition. But it had the effect that not all things took the same time, and starting a long action too soon before someone took a short, opposing action could mean they got to you first.
In any case, I looked at OSRIC and decided it had something to recommend it, but needed tweaking. Here is what I ended up using:
First Round Only:
0) Determine Surprise. Roll 1d for your own side. If the result is a 1, the group is surprised for one segment. If the result is a 2, the group is surprised for two segments. If the result is a 3-6, the group is not surprised. [Segments count as a full round during surprise for melee attacks, but count as normal segments for missile fire or spells, Dexterity Adjustments reduce surprise segments 1:1]
1) Declare Spells and Actions (For example, cast Fireball, attack in melee, flee, etc.)
2) Determine Initiative (Each side rolls 1d for the other side’s initiative. Each party acts in the segment indicated by the other side’s roll.)
3) Party with Lower Segment Roll Goes (Resolve PC actions clockwise around the table, results take effect immediately. Side without initiative can get specific reactions – hitting fleeing characters, receiving a charge with spears, etc. Spells take effect on the segment indicated by the casting time, even if that’s after the other side. If it’s the same time, flip a coin to see if you get the spell off before anyone attacks you.)
4) Party with Higher Segment Roll Goes (As #3, but for the side with lower segment roll)
Repeat until the battle is over.
Note: Spells are automatically spoiled by a hit during casting. Spoiled spells are used up just as if the spell was successfully cast.
Note: Unlike AD&D, we will not split multiple attacks up into before-and-after initiative attacks. Especially for 3/2, this means every other round we need to remember a second attack AFTER everyone has gone. Instead we’ll treat it as one action.
Then I just set times to do anything - pretty much, 1 segment for any given action. Swap weapons? 1 Segment. Put away your shield and mace, and take out your staff and attack? 3 segments (Put away shield, put away mace, ready and attack with staff). So if your initiative was 4, you'd actually get to go on 7.
In actual play, though, I ended up rolling surprise for the other side. I still don't love 1 = 1, 2 = 2, 3+ = 0 but it's simple. Reaction adjustments can negate (or prolong) surprise, but since we're rolling by sides for initiative they don't affect which segment you go on.
Declaring actions ahead of time is something we've done in other games, so it wasn't a new concept to the players. It worked very well - people didn't spend a lot of time trying to decide their best option for right now, because they didn't know what the situation will clearly be when they actually get to go. Maybe the bad guys will be killed by people before them in the order. Maybe the bad guys will force their hand by fleeing or using spell-like powers. You just choose what you hope to do and then we resolve it as your turn comes up. It certainly pushes the pace nicely and encourages finding and memorizing 1 segment spells you can use during combat.
In retrospect, you don't need to set this up with rolling the other side's initiative number. You could simply roll your own side's, and hope for a low roll. It wouldn't materially change things except you'd be excited by a 1 and disappointed with a 6, not the other way around. I may change this for next session and say, roll your own