Mass Effect 3 might be one of the greatest games I have ever played. The rollercoaster of emotions that you will experience... holy hell.

This has gone through the most revisions, but arguably this order keeps the narrative solid throughout. It also assumes that every squadmate made it through the suicide mission. If they didn't please disregard and substitute.

Some tips:

Did I mention how much I adore this game?

If you're looking for character builds, check out this reddit post.

The first few missions are pretty linear until you leave the citadel for the first time, but you will realise pretty quickly how they have to be.

PROLOGUE EARTH -  No companion choice.

PRIORITY MARS - Companions not optional.

PRIORITY THE CITADEL - Companions not required. 

Once you're back on the Normandy speak to everyone you can speak to. Also, if you bought all of the ship models in ME2, you can find them dotted around the ship. They are mostly in the cargo bay and the storage under engineering, but one is in Thane's old room.

RESCUE TURIAN PRIMARCH (Scan the surrounding systems in the cluster.) - James and Liara.

DOCK AT THE CITADEL 
I'd like to give you a recommended order of which elevator platform to choose at any given time, to ensure that you do not miss anything because this first citadel trip is a doozy. This list is by no means detailed in an attempt to be as spoiler free as possible but there could be people to speak to/things to do on each floor. Once you've spoken to someone check the map to see if there's anything else you need to do.

SEARCH KITES NEST CLUSTER

MEET WITH DIPLOMATS - Garrus and Liara.

RECOVER PROTHEAN ARTIFACT - Liara (mandatory) and anyone (my personal favourite is Garrus)

RESCUE THE STUDENTS - EDI and Garrus/Liara.

CERBERUS LAB - Anyone.

SEARCH ISMAR FRONTIER CLUSTER

SEARCH KROGAN DMZ CLUSTER

INVESTIGATE CERBERUS PRESENCE - Anyone

DOCK AT THE CITADEL

DOCK BACK AT THE CITADEL

EXTRACT TURIAN SURVIVORS - Garrus and Anyone (it's a turian heavy mission.)

TUCHANKA BOMB - Garrus and Anyone.

INVESTIGATE MISSING SCOUTS - Javik and Garrus.

CERBERUS ABDUCTIONS - Anyone.

DOCK AT THE CITADEL

PRIORITY: TUCHANKA (THE FINAL MISSION ON TUHANKA) - Take your favourites, everyone has unique dialogue.

Don't forget to speak to everyone.

CERBERUS FIGHTER BASE

SCAN ALL SYSTEMS THAT ARE NOT ALREADY AT 100% (Some will have nothing but it's worth just going through them and making sure you've collected everything you can.)

DOCK AT THE CITADEL

FIND EX-CERBERUS SCIENTISTS - Virmire Survivor/Garrus and EDI

SPEAK WITH QUARIANS - N/A

You might have some people to speak to on your ship.

INVESTIGATE ASARI COLONY - Liara and anyone.

DOCK AT THE CITADEL

DISABLE THE DREADNOUGHT - Tali (mandatory) and your Love Interest. Or, if Tali is your love interest, the person you romanced in ME1. If you didn't romance anyone in ME1, bring EDI or James.

SCAN FOR DR GARNEAU - Your Love Interest and Anyone else (I like taking EDI because she's so present in the lab)

A friendly reminder to talk to everyone on your ship after each mission.

SCAN ANY SYSTEMS THAT YOU HAVEN'T ALREADY SCANNED AND ARE NOT AT 100%

FUEL REACTORS - Anyone

DOCK AT THE CITADEL

SAVE THE ADMIRAL - Tali and EDI

SHUT DOWN GETH SERVER - Tali and Anyone

SCAN THE DIG SITE - Your Love Interest and Anyone 

Another reminder to talk to everyone once you get back to the Normandy. There are so many fun interactions, not just between Shepard and characters, but in the conversations they have with each other.

DOCK AT THE CITADEL

DESTROY REAPER BASE - Tali (mandatory) and Anyone

Talk to everyone back at the Normandy.

RENDEZVOUS WITH ARIA'S FLEET - Solo time, this is a big chunky bit of DLC.

DOCK AT THE CITADEL 

LOCATE SECRET ARTIFACT - Liara (mandatory) and Javik.

Scan any systems you may not have already scanned, and talk to everyone on the Normandy.

SEARCH FOR LEVIATHAN - Your Love Interest and anyone.

COMMUNICATION HUB - Anyone.

INVESTIGATE SANCTUARY - Virmire Survivor (if they are an option) and Anyone.

DOCK AT THE CITADEL

DOCK AT ANDERSON'S APARTMENT

If you have anything left in the journal complete it now before PRIORITY CERBERUS HEADQUARTERS. This is the point of no return.

ASSAULT THE ILLUSIVE MAN'S BASE - EDI (mandatory) and your Love Interest.

ORDER FLEETS TO EARTH

Part one - James/Virmire survivor and Love Interest

Part two - Your Love Interest and anyone you want.

That's it! If you've gotten this far, you've had what I would consider a playthrough with the most cohesive narrative of Mass Effect.

I hope you made some wonderful choices and had an excellent experience. 

And that you get over it soon. 

I haven't.