After spending some time on the Citadel, if you return to just outside the Embassies, near the reception desk, you'll be flagged down by Samesh Bhatia. His wife was a marine killed at Eden Prime, and the military is refusing to release her body. If you go to the Embassy Lounge, just up the stairs to the left of the reception desk, you can talk to Clerk Bosker about the problem. He's the man responsible for greenlighting the release of Mrs Bhatia's remains, and he's also clearly overawed by meeting a great hero such as yourself. Use this to your advantage and talk him into doing the decent thing. Return to Samesh to receive his gratitude.
Worth doing? Probably not. This is another assignment that only takes a few minutes, but all you'll get from it is whatever Renegade or Paragon points you accrue through your conversations.
This is a simple test of your ability to negotiate a solution to a problem. The alien Hanar is preaching on the Presidium without permit, much to the annoyance of the C-SEC officer. How you approach it is up to you - the conflict can be resolved in many ways. You can complete this assignment via practical means at any time, but you'll have more options if you tackle it after becoming a Spectre, since you get a boost to your Charm and Intimidate skills.
Worth doing? While the rewards are minimal, you might as well tackle it since the whole mission can be tackled quickly and in one place.
Wandering around the Upper Wards, not far from the stairway to the C-SEC Academy, you'll be flagged down by Emily Wong, a journalist investigating Citadel corruption. She asks you to pass on any information you may find about organised crime. This is tied in to one of the main story missions - you don't have to be a genius to work out which one - so should you happen to find yourself facing a local criminal, it pays to search your surroundings for anything useful. Emily is very grateful if you do and, with a little charm, you can get a few bonus rewards as well.
Worth doing? Yes. You'll be doing most of the legwork during the story anyway.
Scan The Keepers
After your first hearing before the Council, as you descend the steps you'll see an alien interfering with one of the keepers, those weird silent creatures you see around the place connected to machines. Quiz him about his intentions and you'll discover he's Chorban, a scientist trying to find out more about these enigmatic beings. Such interference is forbidden however (probably best not to muck about with them right next to the Citadel Council then, eh?) but you can offer to help him out. There are 21 keepers spread around the Citadel, so it makes sense to hold off on some of the other assignments until this point so you can scan keepers and fulfil other objectives at the same time. They're easy enough to find, since the area of the Citadel you can explore isn't all that large, provided you search each location thoroughly - they're often tucked away in corners.
Worth doing? Definitely. You get a small amount of XP and credits for each keeper, plus over 1000 credits and 360 XP when they're all scanned.
Jahleed and Chorban
If you want to flesh out the Scan the Keepers assignment a little more, and find out exactly why you're running around harassing green lizard things, then head for the C-SEC lounge in the Lower Wards and look for the Volus called Jahleed. He's convinced that Chorban, the alien who has you scanning keepers, is trying to kill him. There's not much to this assignment, just a bit of to-and-fro between the characters to find out what's going on.
Worth doing? Only if you're curious about the keeper business. There's no reward for this assignment, and the tepid resolution is hardly riveting drama.
Schells the Gambler
When revisiting the Flux nightclub, you'll see this shady character being thrown out. Interrogate him and you'll discover he's working on a device that will beat the casino system. This is one of those moments of moral choice, with different rewards depending on the approach you take. Those with flexible ethics can earn a good chunk of credits with this one.
Worth doing? Yes, especially if you're playing for Renegade points.
While in the Flux casino, investigate the gambling machine near the back wall. You'll discover a strange signal coming from it, which is diverting credits into a mystery account. You need to trace the signal from relay to relay though, rather annoyingly, you have to go into the Assignments screen to find out where to look next. The directions are often vague, and more than a little misleading, so here's some help - first check the lounge in the C-SEC Academy (it's where you find Jahleed), then go to the financial district and check the machine behind Barla Von. Finally, go to the right hand room in the back of the Emporium. You'll discover the source of the problem, and find out that it's not really one for negotiation. Save your skin with some quick button matching.
Worth doing? For completion's sake only. There's a lot of running around with no tangible reward.
These are side quests that must be activated on the Citadel before you can investigate them fully after you set off into space. More complete descriptions will follow with the relevant galaxies.
As soon as you arrive at the Citadel, hack the computer console in the room where you start. You'll discover a message about mysterious energy readings from the Argos Rho cluster. Maybe you should drop by when you get the chance?
In the Embassies, drop by Executor Pallin's office and hack his computer console. He doesn't seem to mind. You'll discover a spam message about a biotic commune. It sounds innocent enough, but it never hurts to check...
Missing Survey Team
Keep your ears open while travelling in those interminable elevators. In the C-SEC Academy you should hear a news report about loss of contact with a survey team in the enticingly named Hades Gamma Cluster. Why, nothing bad could happen somewhere with a name like that! Once you've heard this news, the assignment will appear in your list.