Can you find the make and model of the camera?
Most older SLRs have a light sensor on the front of the camera, looks like a solar panel of sorts. On some cameras you can't really see it.
You need to use your camera's metering tools to help you determine proper exposure, or buy a light meter that you can hold in your hand.
On my old Pentax the light meter display wasn't digital, it was a needle moving on side of the viewfinder that I could see as I was taking a picture. You should be able to see it move if you move to and from a brighter object.
Newer cameras have digital displays, some just show a + or - depending if you are overexposing (too much light) or underexposing (too little light ). It really depends on the camera.
From what you have told me, sounds like that meter isn't working because you should have noticed it. The meter is the only thing powered on older SLRs so check at the bottom of the camera and find the battery slot and try to get it replaced see if that fixes it.
Otherwise if the light meter is busted (rather common) you need to grab a hand held one off eBay or something, doesn't have to be too fancy.
If you are shooting automatic and it doesn't have a working meter I imagine you would get some odd exposures.
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You have to adjust aperture and shutter speed until that meter gives you an OK.
This isn't exactly random how you do it.
Tho settings "Automatic, B , 1, 2, 4, 8, 15, 30, 60, 125, 250, 500, 1000" you mentioned are the shutter speed. Auto for .. auto. B for bulb meaning it will stay open as long as you keep your finger on the shutter, only useful for certain things. Then you go 1 second over the rest so 1 sec, 1/2 a sec, 1/4 a sec to 1/1000. Thats the time you allow the film to be exposed.
So first you set your aperture to what you want. If you don't have a lot of light you use a lower f number. This also creates a shallow depth of field.
If you have a lot of light you go higher in the f number.
Next you adjust your shutter speed to counter balance your choice of how much light to let in the lens (aperture). You need enough to be able to hand-hold it and not get blurry pictures which the general rule is, don't go under 1/60. So you look at your meter and set it to 1/60 and it says you are overexposing, you move up to 1/125 and re-check.
Once you actually start shooting you will know what will work for what light.
There is also the "sunny 16 rule" that might work if you are w/o a meter
http://www.camerareview.com/templates/sunny16.cfm go ahead and read up on that.
Also, you mentioned filters, some block part of the light, and some cameras don't measure light going into the lens, since the sensor is somewhere else, so take the loss of light into account when setting up a shot.
Sorry for the long rant, hope this helps some.