And don't let Wounded Ronin scare you. It's ok to mess up every now and then unless you're players are raging assholes, in which case why are you gaming with them? The important part of screwing up is to admit it when you realize it and fix it if possible. Don't bother with too much retconning unless it's a huge problem (like the difference between 2P and 7P). A few examples of what I've done:
- If you miscalculate someone's attack and they deal more damage to a PC then they should, just wipe that damage off. If you're not sure how much, go with the average + 1. It fixes the problem that probably would have occured, and the +1 makes it so that if the player complains they look like they're being a jerk.
- If for someone reason someone isn't taking as much damage as they should have because of a miscalculation, either add the damage, or if it's too late shift that damage over to future opponents.
The important part, again, is to admit it and fix it. Everyone makes mistakes, but the GMs that try to act as if they didn't don't get respect.
The next important thing, which in my mind is even more important than rules consistency (YMMV) is reality consistency. Actions should have consequences, both good and bad. The important thing is that those consequences are logical. It's one thing to have one gaurd out of 30 know somebody capable of hiring a team to hunt down the PCs that killed him, but if every third gaurd is Lofwyr's godson your players are going to laugh at you.
cybertrucker is right about railroading: it sucks bigtime. However, for the first couple of runs it might be ok. If your first few runs are simplistic and fairly linear, you can tell your players ahead of time that they're like "practice runs" and they should be nice enough to follow the plot for you. Once you've got the hang of running combats, hacking, astral scouting, and the tons of other things that a GM has to do in his games, then you take off the kid gloves and go for the more complicated and player-driven scenarios.
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