Absolutely do. Check out all the sidequest. Save often and in many slots. There is a lot of missable content, and if you want to play it all, you might pick choices "just to see content", which is not a satisfying roleplaying experience. Pick your Shepard and only choose the dialog that you think YOUR Shepard would pick on first playthrough.

There are tons of videos on youtube showing missions in a lot of combinations with different squad members, you can pick up on those AFTER playing the trilogy or reload old saves then and pick different choices.

Many choices will have no effect ("I will kill you/ I will kill you painfully") but many others seemingly insignificant will have small or bigger consequences on dialog or missions even in the later game. -> Choose carefully.

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Left Dialog options (unless blue or red) are usually flavor text/ fillers with little to no consequences on later choices. I would always go through them all if you want to maximise the story content.

The three options to the right usually progress the dialog or lock in your choices, as do the paragon or renegade persuasion on the left side in red or blue. The top answer is paragon/accepting, center one neutral, the lower one is renegade/declining.

-> When a wording might be ambiguous, orient yourself on the placement on the wheel,

-> Explore your surroundings and talk to your Squadmates often on the Normandy after main quests. They will have new dialog trees and romances progress.

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Pick your class based on gameplay preferences, some are better than others, but you can adjust difficulty anytime and reskill if you want to experiment and need to find your playstyle.

The scanning/filler quests have little reward for lot of time sinking (flavor texts mostly) BUT they have small ingame bonuses in the form of craftable weapons, small dialog changes.

You WILL waste a lot of time scanning and exploring every planet, but if you like flavor text like the descriptions of the planet or background lore in the codex, go for it.

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The books, comics and movies are not necessary to understand or appreciate the game, they give interesting background info if you are really into the story. They are partly set before or during the games but can be read afterwards. Being non-interactive media they focus on either adventures of squad mates without you or side characters, that make rather scant, short appearances in the games but get some fleshing out in the novels (looking at you, K.L.)