I'll be running book 1 of RotRLs soon, but I'll only have 3 players, all new to Pathfinder. I read in another thread that 15 is standard for a four man party so how much for 3?

Currently, I'm thinking 20, but would that make up for the lack of a player, or would the best way just be to use the controversial GM PC?

You may just want to trim down some of the encounters. If there are four goblins in the written, have the players face three. Otherwise, the players will advance slightly faster, as there are less ways to split, so that might help balance out too. I recommend the above with 20 point buy.

I'd use a GMPC and 20 point buy anyway. (this is what I play in our ROTRL game... the buffbot and reader of obscure texts)

The big issue with GMPCs is spotlight stealing.

So make a band-aid cleric that follows the group around and occasionally gives advice. Could be a normal cleric or an evangelist (for more boosting like a bard). In melee combat, just does aid another with a longspear.

Sample Human (20 pt)
STR: 10 DEX: 10 CON: 10 INT: 13 WIS: 19 CHA: 13
Feats: Scribe Scroll (for extra support), Extra Channel (for more healing)

Personally I can't support the GMPC. I've seen it work well a few times, but usually it's not worth the headaches.

I'm about to kick off RotRL for a group of three PCs. One is VERY skilled with RPGs, one is very experienced but less immersed in rules, and the last is a casual gamer.

I ended up going with something roughly close to 22 or 24 point buy. Not sure. I averaged some 4d6 drop rolls ;)

However, I'm using either slow or medium XP progression, and if things are going too easily, I'll add more challenges. I find it easier to just add bits and pieces here and there and to throw in extra challenges--potential for items breaking, higher chances of failure on crazy plans, etc.

I've been running with three inexperienced players. Since this is my first AP, I'm not deviating a lot from it as written. I let them have a 25 point buy with hero points but no GMPC backup, they're dividing 4 players worth of XP among the 3 of them, and they've been doing fine. We're about to end book 2 and they've had roughly the same difficulty as a normal group from what I see on the forum.

OK, maybe a little easier since I still tend to forget that bad guys carry potions.

Personally all of my games are run with PCs at 25 point buy. I have 8 players and the APs are hard for me to run with that many. All my players are exerienced though and we all prefer the 25 point buy. My thought is the PCs are heros so make them heroic.

15 point buy is Mo fun.... as long as EVERY NPC you run into isn't stronger, smarter and wiser.

OLD NPC used to have straight 10 stats, or never had stats over 14 unless he was REALLY strong or smart..... I despise Paizo NPC stats...it ALWAYS seems they have a clause "this Npc was built with a bazillion point buy because he/she is cool awesome and fun"

I'm getting REALLY tired of that.

I'll be running book 1 of RotRLs soon, but I'll only have 3 players, all new to Pathfinder. I read in another thread that 15 is standard for a four man party so how much for 3?

Currently, I'm thinking 20, but would that make up for the lack of a player, or would the best way just be to use the controversial GM PC?

We alsways use a 20 point buy (four man party), but with three, I would sincerely reccomend that you not only grant them a 25 point buy, but you seriously consider giving them Ameiko as an NPC/GM mouthpiece for the duration of the campaign.

If stats were rolled 4d6 drop 1, the average build's point buy would be about 19 points, and that's including the very rare, but possible, illegal (through point buy) results that include stats less than 7 (using the extrapolated point buy for values less than 7).

So 20 is my view of how it should be generally, based on statistics. That said, if you do 20, don't do hero points. Well, that's my advice for a "normal" party... for 3 PCs, maybe hero points will be advantageous.

To compensate for the lack of a PC, I'd recommend that you encourage optimized characters, but if that's not practical, or not your group's thing, an alternative I'd recommend is keeping the party a couple of levels beyond the expected progress (and just award levels where the book says they level). And Toughness as a bonus feat can't hurt. Another option is to use less sophisticated tactics for enemies.

Edit: by the way, this AP includes a substantial amount of treasure. By my calculations through 10th level, a party of 4 10th level characters receive approximately 140% of the wealth the Wealth By Level table expects them to have. So this should mean they have a significant chunk of change for gearing up. Depending on the classes, that could be a huge boon for them.

Going to be running today, and going to take the advice of 25 point buy. If they need it, I'll add either Ameiko or the ranger elf as a GM PC. thanks for the advice everyone who's posted, and Happy New Year.