Careful when you move close to the control point - there is likely to be a rather large pack of dogs close by and if they catch the scent of you they'll likely attack. If they do, try not to kill them all - you may soon pick up a mission to do just that, which can't be completed if you've already killed them all.
At the control point you'll find Sergeant Kitsenko. He can tell you a bit about the Bar area and also provide you with an optional mission - Purge the dog lair. This is an easy and quick mission to do, and you'll be given a Meat Chunk artifact as a reward - not bad for spending a minute of your time. The mission basically requires you to kill the aforementioned pack of dogs.
Please note that combat within the main Bar area is off limits - if you kill someone (apart from the dogs), even in self defense, may result in other stalkers becoming hostile towards you.
The 100 Rads Bar is located to the south of the Bar area, west of the hangar you'll have to go through from when you are approaching from the control point. Inside the 100 Rads you'll find the Barkeep, who'll not only give you storyline and optional missions, but also functions as a trader. You can also find a number of stalkers there, and most of them have optional missions you can pick up.
You may run into a bug regarding the Barkeep. As you may have noticed, the Barkeep walks back and forth behind the bar. Sometimes he stops in front of the TV - and this is where you may encounter the bug. Sometimes (very rarely, though) he seems to get stuck, or just doesn't move from that point. Since you can't "reach him" you wont be able to either talk or trade with him. If you encounter this bug, your only way to fix it is (unfortunately) to load an earlier savegame.
Update: Our local resident, T.A.L.K.E.R., has hinted that just saving and loading a game when you encounter this bug is enough to "fix" the Barkeep, so try this before you load an older savegame.
The Barkeep will give you a Gravi artifact as a reward for the Camp defense mission that took place in Garbage. He can provide you with a number of optional missions - refer to this page for a complete list. When you talk to the Barkeep will be able to tell you a bit about Strelok, Ghost and Fang, and tell you a somewhat long story about the "wish granter". As I explained earlier, the main storyline missions are not timed so feel free to deliver the documents to the Barkeep and pick up the next mission.
Mission: Find the documents in the underground lab
To get into the lab you'll need two keys, one of which the Barkeep will already have provided. You'll need to obtain the second one from someone called Borov in the Dark Valley... and by "obtain" the Barkeep actually mean you must pry it from his cold, dead hands.
Your next mission briefing.
This may be a good time to buy a new weapon from the Barkeep, namely the IL 86 assault rifle. Although, compared to the Akm 74-2, it has less accuracy, handling and rate of fire. It comes with an integrated scope which obviously is a nice feature, especially at this point in the game. The IL 86 uses a different ammunition type, 5.56x45 rounds, which can be bought from the Barkeep - in the upcoming areas (Dark Valley, especially) you won't find this type of ammo, so if you decide to pick up the IL be sure to buy as much ammunition as possible. You will get your hands on a PSO-1 scope that will fit on your Akm 74-2 so if don't wish to part with that just yet, you can just bring that along as your primary weapon, or backup in case you run low on ammo for your other primary weapons.
Travel light because the Dark Valley, like many of the other areas, is likely to turn up alot of loot including artifacts and possibly a unique item or two.
Now you have different options available to you - you can simply proceed directly to the Dark Valley if you wish, or you can pick up some optional missions from the Bar area and explore some different areas. If you still haven't picked up the PSO-1 Scope you can actually do so in three places now that you've reached the Bar - you'll still be able to get it in the Dark Valley; you can also pick up a Vodka bottle and head into the Army Warehouses area and locate Screw at the Freedom HQ - he'll give you a scope in exhange for the vodka. Finally you can head into the Wild Territory - this is a tougher place, though, since you'll need to take the scope from four Merc snipers.
As you may have noticed with the inventory of Sidorovich, it is actually randomly generated (more or less) and will replenish when you leave the area and come back later; the same goes for other vendors and can be used to eg. buy ammunititon that you're low on - simply buy as much of the ammo as you can, leave the area and come back, and the vendor should now have more of that particular ammunition available.
The next section is about the arena - a place where you can fight different opponents and win money. If you don't have any interest in that just skip ahead to the next page.