Pedrop says:
... Any good guidelines? That wouldn't require to read the whole book about it? ...
tl;dr
Well, reading lots of books about it is a good option. :)
Be open to learning, and play lots of games. Talk about it with your fellow players (GMs are players too). Adjust to the various games' different styles. Patience and Practice. Listen to
TheGenerator.
Longer 'guide':
Pedrop says:
... I think it is very hard for me to figure it out how much I should be proactive? ...
It is a learning experience. Don't rush it, we are patient. Also don't get offended when we correct you. Ask questions and adjust for next time. Just like you did here.
Pedrop says:
... don't have any real experience with
playing(maybe I still think about those games more from GM-wonna-be perspective?) ...
Switching from GM-mode to player-mode can be hard. Maybe (in this example) think about how you would feel as the GM if the players said: "GM says we have a problem of not having a truck... let's just say we
have a truck. That solves that problem, right?".
GMs can make good players, often they know what sorts of things cause problems for GMs and know to avoid them. But they might also have not encountered a particular problem and fall right into it.
Do you see, from a GM perspective, the specific issue happening here? It is not a big deal, and does fit with my style (if the players don't like a scene/encounter we skip it), but we were, maybe, doing a thing here and you decided, on your own, to 'be proactive and skip it' to 'move things along' (after everyone else had been waiting for you to get back from the weekend (which we knew about from the start), but was also the reason things were not moving, and only mentioned now because the previous time you were over-proactive was also after a weekend away).
Having Bob come in and solve the lack of vehicle was a potential solution if people wanted it, but you stepped on the scene and killed it, without finding out if anyone wanted to play out that scene or do an in-game, by-the-rules solution. It bypassed all RP and mechanics.
Pedrop says:
... They say you should be proactive in PbP format ...
I don't know who 'they' are, but one should be proactive in all RPGs, we are not passive observers along for the ride. This is not a story-book provided by the GM.
Pedrop says:
... there is no time to establish every detail ...
True. However, that also means that details that
have been established --in this case, that getting a truck would not be easy-- are kinda important --in a Checkovian way-- honour them.
Pedrop says:
... You should make your rolls in advance ...
That depends very much on the rules of the game. That sounds like DnD advice. We are not playing DnD.
How would you roll in advance here? What would you roll? We first need the fiction to be able to work out what to roll. Do you see how your haggling with Bob over the price could not have happened with a roll-first mentality? We first needed the fiction of what you were doing so we can work out the applicable Skills, then we needed to set the Difficulty, only
then can you roll.
Fiction First.
Pedrop says:
... to make game faster ...
Rolling can slow a game down, but rolling wrong breaks the game and that slows it down even more... sometimes to a complete halt. To speed things up I prefer to have as little rolling as possible, but rolling is fun, and an important part of the game, so there has to be some.
A situation where the players do not roll can place too much power in the hands of the GM. The dice dictate the outcome/cost/consequence, and without dice the GM just decides, and that can feel unfair. "We were warned to not go in, but we walk in anyway.", "Rocks fall, you die!" does not feel at all good. "...we walk in, rolling to be careful and avoid the deadly trap... and get a 1.", "Rocks fall, you die." is a very different feeling of blame, that is clearly not the GM's fault, it was the dice.
The dice help everyone agree on how bad things are. It also makes a difference who rolled the dice: Players want to feel 'in control of their own characters', so even having the 'GM roll for them to speed things up' feels wrong. Same dice, same odds, but different feeling.
TheGenerator says:
... maybe a driving or mechanic roll would be something that can still make the van a challenge? ...
Rolling now, after we have seen that he has a van, and that he got it to your location, is sorta pointless. The problem is known to be solved, what would the interesting consequences be?
Pedrop says:
... the GM can discard them if they are not needed ...
That, again, very much depends on the game and its rules. In something like PbtA where 'nothing never happens' every dice roll must be acknowledged (by the rules), some even provide XP and you don't want to take that away from the player after they have got exited about it.
I was recently dragged into a discussion on GP Discord about MotW and XP on a miss, and people were complaining that some players 'roll weak stats in safe situations' to get free XP. Which I had not encountered in my games, at least not for very long. Firstly I don't allow players to roll before they have been asked to --so no 'rolling without risk'-- and secondly, in most PbtA the rolls/Moves only trigger when there is danger. I regularly have players ask "Can I roll
Read a Person'" and I point them to the text of the move, telling them that "the situation did not seem 'charged' but if you roll --by the rules-- it
is, (maybe they will notice you studying them and get upset that 'you don't trust them'?)". After the first time they 'die' from a failed roll in a 'safe' situation they stop that cheating, but at least they got the XP.
Look to the game rules for that. I don't discard rolls, same way I don't encourage post-and-then-edit. Everything matters.