The purpose of this post is to describe the process I use for getting correct LTMs for the initial season of a league (or for any single season replay). It uses an undocumented "feature" of the LTM adjustment process that even some veteran players may be unaware of.
In the League Setup portion of Game Setup, on the Strategy Page, there are League Totals (LTs) and League Total Modifiers (LTMs). Please read up about these in the manual, if you are unfamiliar with them and how the game uses them (also how the game adjusts them before each new season).
The LTMs always start out at 1.000 in a new league (this hasn't changed in OOTP10), which means that the stats produced in the first season (and, to some small extent, even in a second season) are likely to be unrealistic. Some of the worst problems in this regard (e.g., SBAs) have been improved in OOTP10, but the problem still exists. The standard recommendation has been that people sim out a couple of seasons (so that the automatic LTM adjustment process can kick in) before they really start playing, but many OOTP gamers don't want to do that. I know I didn't.
Here are the steps:
1. Create your league. I suggest using some other name for your league than the one you ultimately want (because you will be discarding this league eventually and you don't want it pre-empting the name you want to use). Get the league set up for play to your satisfaction. Save it.
2. Create a copy of your league. One way to do this is by using the "Make Backup" function in the game menu. This function makes a complete copy of your game, using the same name, but puts it in a different folder from Saved Games. The other way to do it is to go out to your system and make a duplicate of your league folder in Saved Games (which is why you want to save your league before making a copy). This copy is the version of your league that you will actually end up playing, so be sure you have copied it fully.
3. With the original version of your game still loaded, go to the League Setup Strategy Page and uncheck the "Automatically adjust league totals modifiers after each season for historical accuracy" box. If it was already unchecked for some reason, leave it that way.
4. Select the option which directs OOTP to Auto-play (sim) a complete season until "... PLAYOFFS BEGIN". Since this version of your league is only for the purpose of gathering LTM-related data for your real game, there are a lot of steps you can use to speed up this sim. For example, in the Game Preferences, set Auto-play display to "simple dialog". Turn off injuries, trading, financials, Spring training, all-star games, drafting and anything else not necessary for producing stats. I also find it is faster if I make myself commissioner only, and not a team manager as well.
5. When Auto-play is done, go to the League Setup Strategy page. You will still see 1.000 in all the LTM boxes. At this point check the "Automatically adjust league totals modifiers after each season for historical accuracy". You will see the LTMs change in almost all of the boxes. What has happened is that the game has calculated the LTMs that should have been used to get more accurate results for the season you just simmed. Those are the numbers you want for the league you intend to play. Write them down, making sure that you keep track of which numbers go in which boxes. (Side note: if by some chance you simmed this season but forgot to uncheck the "Automatically adjust ..." box first, it's OK. Just uncheck it, sim one more day, then recheck it).
6. Load the copy of your league, giving it whatever name you want (this is pretty easy with the Restore Backup function). Go to the League Setup Strategy page, and replace the 1.000 LTMs with the numbers you wrote down. Also, check the "Automatically adjust league totals modifiers after each season for historical accuracy" box if it is unchecked. Save. Make a backup (just because it's a good idea). You are ready to play. (Side note: if you want to be really thorough, enter these same LTMs into the appropriate boxes for each of your minor leagues. This is what the game does automatically in the LTM adjustment process. You will get better stats in your minor leagues, though they will still be more unrealistic than many gamers would like. Nothing I can do about that.
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With a fast sim, all this can be done pretty quickly (30-40 minutes perhaps). As a result, I think there is no reason why OOTP gamers should have to compromise on what they get from that first season.
Note for OOTP veterans: the LTMs that you get from this technique are not the same as the adjusted LTMs that the game automatically creates at the start of each new preseason. The latter are calculated based on the previous season's results but adjusted for the coming season's historical stats. You can check this out by getting LTMs using the technique above, then simming forward to the next preseason. You will see that the LTMs have changed. In contrast, the LTMs you get from this technique produce realistic stats for the season just simmed if you use them in a cloned version of that season.
As noted in later posts in this thread, this technique does not seem to work correctly for errors. I don't know why, and perhaps in some future patch this will be fixed. The LTMs you get for errors are better than the 1.000 default settings, because you will get a better distribution of errors by position. But league/team totals for errors will likely be off from historical stats. By checking the historical record, you can calculate a manual adjustment for yourself, if you wish.