I have bought my first DnD adventure, Dragon of Icespire Peak, mainly because I wanted a good opening adventure to introduce some new players to the game.
However the module uses milestone leveling with clear advice to increase to level 1 after quest 1 and then increase based on the successful completion of quests thereafter.
I am planning on this to be an opening intro to a wider campaign I have planned and have tweaked the setting accordingly however I generally run my campaigns based on experience points, largely because I run a very open world players can do anything including ignore the main story, type of campaign. I don’t have anything largely against the way players will level through the adventure but I don’t want them to get to level 5/6 and then suddenly start handing out XP as we move into my own material.
Are there any clear rules to converting the milestone based adventures into XP style games? I can easily work our roughly how much XP the various monsters will return and then work out what completing the quests/role playing bonus should give to allow the players to advance at roughly the same pace but are there any official suggestions as to how to do this?
Just to add some clarity, I will be running for 6 players, and these are mainly new players so I want to be able to use XP to reward role playing and good gamesmanship as well as just completing the quests and killing stuff.
As suggested by a comment the way I hand out XP is very much based on rewarding roleplay and good gameplay as opposed to just monster killing. If a group of potential enemies would give 350XP if killed but the party resolve or avoid the encounter in a different way to combat the odds are I will reward with the same amount of XP. I also give a large % of XP for how the players roleplay social encounters, or come up with clever ways to deal with a situation.
Milestones take away this ability to reward player behavior throughout the quests instead simply rewarding at quest end.
Best Answer
You're better off sticking with milestone levelling
The upsides of this are of course that you don't have to mess with the pre-created module and can just play it as-is, but that's not the reason I'm suggesting this. I'm suggesting this because of something you mentioned in comments:
I completely disagree with this reasoning. In my experience (no pun intended), I've found that games that make use of XP tend to encourage players to pick more fights and rely on combat, fighting everything to the last, because the more things you kill = more XP = faster level progression. It tends to discourage more roleplaying-based solutions and clever planning (besides how to kill the most enemies with minimal risk, but still expecting full XP for it).
However, I've found, both in using milestone levelling and being a player in games that use it, the use of milestones tends to encourage players to forget about how they're going to get to the next level, allowing them to engage in the story more, roleplaying their way out of combat if it better fits the narrative, being more creative, focusing on the story precisely because they trust that you'll hand out the next level up when the story calls for it, freeing them up to progress with the story in whichever way they please (i.e. not just fighting everything for XP).
The accepted answer to Does 5e address the murderhobos problem? proposes using milestone levelling as a way to reduce murderhobo style play (assuming you agree with OP/accepted answer).
But what about when I start using my homebrew stuff?
I'd recommend still using milestone levelling, even if your game isn't going to necessarily "follow a strict story" in a railroading sense. However, your party will still be achieving something and when you feel like they've achieved enough since their last level to deserve the next one, that's when they level up. This still allows you to run the game with player decisions front-and-centre, allowing the party to decide where to go and what to do next.
In a couple of games I'm currently running, I'm effectively using milestone levelling, but behind the scenes, I'm also lumping together how much XP the various combat encounters would provide so that I know that, when I decide the party have achieved enough in an in-game narrative sense, I can also double check that they've also earned a sizeable chunk of "XP" for the level to feel justified.
This prevents me from handing out levels to frequently, or holding out on the party too long. I don't care if they earn exactly the XP they needed (otherwise, I might as well use XP levelling), and effectively whatever they don't earn via XP they've "earned" via roleplaying and story progression, but it's more of a sanity check so that I have more confidence in how often I hand out levels.