Engaging your Players
One of the hardest lessons I had to learn as a DM was that each player has their own favourite parts of D&D. I love the game as a whole and I couldn't understand people playing the game just for the combat or the puzzles. There are those out there that play Role Playing Games who don't like to role play!
I have wasted a lot of time and effort on some of my players trying to get them to be something they are not. I have created scenarios to encourage role playing for people who rewarded my efforts with active noncompliance.
I placed the characters in a position where they were in jail and the non role player was the only member of the party that wasn't gagged. I was trying to see what they would do to try and get out of a bad situation. His response was to go to sleep in his cell.
I was left trying to come up with a solution to the problem myself, me the DM. It left me with a bad taste in my mouth and to me made the adventure seem constructed and linear. I don't want my players to feel like they are along for the ride and the story is going to happen regardless of their input.
After a while I realised that I was in the wrong in this situation, I was being a bad DM and I should pick my battles. I shouldn't have rushed in with a scenario that was pivotal to the storyline, what I should have done was have small points where the character is away from the group and gently coax the player out of their shell. Using interactions with shopkeepers and NPCs in bars should've been my first port of call.
Another example is the player who treats shopping as a purely mathematical occurrence or even a distraction instead of a conversation.
'I'm just going to buy ammunition, it costs this in the DMG, I've marked it off my sheet.'
I plan inventories of vendors somewhat and have an idea of the character who owns the shop. I let the players interact as much as they want, however, if they talk and ask questions they will find the full extent of the merchandise for sale including magic items and improved equipment. After a few occasions of buying inferior gear the player should get the hint that there is more to the market place than what's on the surface!
As a general rule I will now no longer take on new characters who don't have a backstory written out. This process is key to the player knowing their character and the DM knowing how to appeal to the character.
So the lesson here is pay attention to your players and work out what they like about the game and then gear sessions towards everyone having fun. However, there's no harm in pushing players into new scenarios because you might spark a new favourite playstyle for them!
May you roll well!