The first thing to look for in Shamirik is Sandra. She's from Avernum and wanders around the eastern end of Shamirik and the southwestern corner of Lorelei. She'll tell you to talk to Commander Johnson about the Bunker.
Next head into the eastern shop in the row that faces the North Gate. This is the food shop, which is run by Ginny. Ginny will talk to you about a ring that she gave to Sloan, an archer. So go find Sloan, who usually wanders around this block of shops. He'll tell you he lost the ring outside the walls in the southwest corner of town. Go down there and get the ring and then return and talk to Sloan. He'll ask you to return to the ring to Ginny. Doing so completes the small quest.
Now go to the shop at the western end of the same block. This is Grove's shop. He sells weapons, and will also augment items for a fee. Grove is also one of the best places in the game to sell items, since he gives among the best prices. I've never found anyone who pays more actually.
Hiding in the bushes west of Grove's shop is Grassi. He'll sell you some alchemical recipes, though you probably already have them all by now.
Once you've done talking to Grassi head through the door just west of him, and then north through another door. When you enter the room a band of Troglodytes will break into the room. Be nice and help the soldiers out. The door in the northwest corner leads out to the inner wall, which is what I call the area where cities put soldiers to watch the walls. The door to the east leads to a room with some really nice items. Unfortunately there's also a guard so you can't take them, but it's nice to look at anyway.
The next door to the north leads to a small storage area, containing a door leading north to another storage area. You can find the Xian Shrub in here. It's pretty useless, but if you're into collecting all the Xian items...
Now head back into the courtyard and up to the building east of Ginny's shop. This is the temple for Happy Thoughts or some such thing. It's run by Ellyna, who provides healing, as well as selling a few priest spells, a couple of which you probably don't have.
There's another block of shops just south of the first block. The northernmost shop in this block is Ballard. Unless you need some Magic Lockpicks there really isn't much point in visiting him. The middle shop is actually a training hall, which is run by Starcap. After calling you a suck-weasel, he'll give you a quest to find Zang. Zang can be found in Moon. The last shop in this block is run by Isaac, who's a fletcher.
Now head into the building to the west of that block of shops. This is the inn, which is run by Quinn. Buy some bourbon, and then buy her rumor. It will eventually lead to the Black Halberd, which is, in my opinion, the best pole weapon in the game. Sitting at a table in the corner is Ehrenfeld, who's shop was destroyed. He's an armorsmith and will sell you some of his wares. Head into the hallway of the inn and go through the second door. This is Ehrenfeld's room, and you can steal some things from the dresser, just remember to close the door first. You can ignore the warnings about traps.
The row of rooms along the southern wall are mostly apartments. The western room has a trapped dresser. Opening it will release a noxious gas which will poison your party, but it contains a couple nice items. The last room before the gate belongs to Spragins. He'll identify your items, and he also sells some Mage spells, again, a couple of which you probably don't have.
Now head up to the southeastern corner and into City Hall. Mayor Knight's office is to the south. He'll give you a quest to go talk to King Vothkaro in Castle Troglo, but first you need to get permission from Supervisor Levin and Commander Corrie. Supervisor Levin is also in city hall, in the northeast room. He'll demand a bribe of 1000 coins for his permission. I've been told that if you have a high enough reputation you can threaten Levin, or try to reason with him, at least. Save your game before attempting to do this, as I'm not sure what will happen if your reputation isn't high enough. Thanks to Dirty Nephil for pointing this out. Levin also serves as the Job Dispatcher. I'll get to Commander Corrie in a second, but first I want to finish City Hall.
In the southwest corner of the mayor's office is a secret passage leading to the treasury. There's a couple really tough traps in here, and you'll need at least 29 Tool Use skill to disarm one of them. There's a decent amount of coinage in the chests if you manage to get through.
The last section of City Hall is the library. There's an Arcane Blow scroll on one of the bookshelves, and a locked door. Behind this door is the reward you'll get when you complete Mayor Knight's quest. It's a spellbook which teaches Dispel Barrier Lv.2. This is very important because you cannot buy this spell in the game, and, in fact, won't ever learn it at Lv.1.
Now head over to the northeast corner. This is the barracks, and you'll have to go through a door in the first room to the east, and then head down to the southeast corner and through that door to find Commander Corrie's office. Commander Corrie wants you to complete a quest for her before she agrees to let you go on Mayor Knight's quest. She asks you to destroy a big Troglo Altar in the mountains east of Angel's Rest. Be sure to ask her about the Ritual of Sanctification, and she'll send you to Softport to talk to Nydia.
That finishes up Shamirik, so now we're off to Softport to find Nydia.