Rear Derailleur Mounting Bracket

[Carrera]

Just thought I'd ask the following: First thing I noticed about the clapped out bike I'm fixing up was the derailleur mounting bolt was loose. Seems as if there had been a crash and it may have been the derailleur that smashed against the rear wheel and buckled the rim. I have a new wheel now (painful financial process) so I took the derailleur off to check for damage and to clean.
Now, I'm not looking forward to the process of fitting the derailleur and getting all the gears to index. I bet it will take me ages to get it right. I did test the damaged shifters and can confirm they are mechanically sound. So now it's a matter of connecting the derailleur in close enough position to be able to pull cable and move the chain to the largest cogs.
Hence my first question. I'm not at all satisfied again with my book which still doesn't clearly clarify position of mounting bracket on frame. I'm already aware this can be bolted on at angles or at a right angle. No real apparent markings which confuses me. It's a rapid fire Shimano rear derailleur. I think I can handle the overall set-up but it would help to know how to angle my mounting bolt which is just an allen key that bolts through the frame hanger hole and tightens..
I already found the mounting point pivots on some sort of spring. Are there any marks I can line up before tightening the fixing stud?

 

[alfeng]

Check WWW.PARKTOOL.COM for the information which you can't find in the book you bought.

Post a picture of the specific mounting bracket + area of he frame to which it belongs AND/OR to any other "part(s)" to which you are referring.

 

[Carrera]

I've experimented quite a bit. My original derailleur appeared to be clapped. It wasn't springing the chain back on release shift, only going up in tension. So, not wanting to buy an expensive new derailleur, I contrived to "lift" one from another bike (a road bike). First I had to dismantle and clean the derrailleur as it was totally filthy.
I fitted it and where I'm at now is the chain is way too slack. I tightened it by removing some links but it's still too slack. So now I'm hoping the shifting will get better with a tighter chain and I'll remove some more links tomorrow.