Alterations

I am wondering if anyone knows of any good resources for learning how to do alterations.  There seems to be a lot of books written on how to alter patterns (I even own one!) but I can't seem to find anything on altering store-bought clothes.  Some things I have been able to figure out on my own, but others are trickier (taking in clothes that are too big, for instance).  Are there any books written on this subject? 
Thanks for your help!

The way I alter my clothes is to put them on inside out, mark the areas / existing seams that are too big with pins or chalk, and then do a long basting stitch. If it's not right, you can easily take it out with long stitches.

It gets trickier if the shoulders are too big, then you have to remove the sleeve, carefully cut  away the excess, following as perfectly as you can the existing shape, then put the sleeve back on.
I hope this helps!

Thanks for the tips!  That will help me with some of the alterations!

Here are my other questions if anyone out there can help:

If I want to make the waist smaller on pants with a waistband (like a pair of jeans)- would I take the waistband off at the side seams, take in the side seams and the waist band, and then put the waist band back on?

What if I want to take in the sides of a shirt - I can easily take in the sides, but what happens at the sleeve?  If I take the sleeve off and then take in the side seam, then the armhole is no longer big enough for the sleeve, I could make the sleeve opening smaller, but that might make the shirt too tight around the arm.  Is there another way to do this? 

I am wondering why it is that no-one writes books on altering ready-to-wear anymore?  Everything I found at amazon or chapters was in the used book section and published in the 70s or 80s (and had an unaffordable price tag). Even my local library doesn't have any books on the subject.  Where do people who do alterations for a living learn their trade? 

Wow! I sew and refuse to alter unless I'm altering a pattern before I cut fabric. I'll hem pants and do simple things. I think that for your time ratio you might be better off buying a new pair of jeans with the right size waist. Jeans have a continuous waistband and so to take the band in would make it bulky and maybe uncomfortable.

There is a great online book from the 1940's which details many aspects of sewing and fitting clothes. This has helped me tremendously to understand what's going on with different seams, etc.

http://vintagesewing.info/1940s/42-mpd/mpd-toc-long.html

I've also learned a lot by trial and error. Shirts with darts are easier to alter, waistbands often require a lot of disassembly before making them smaller.

Wow!  That's  a great link, thanks so much!  My grandmother used to do alterations ( I know she often said she would rather make something from scratch than to take something apart and put it back together again, but I'd still like to know I could do it) and I thought it would be a great skill to have.  Thanks everyone for your input!

Hi I'm a newbie to the site.
I would not suggest taking in the pants and the waistband in the same area.  It leaves too much bulk with all the seam allowances. Take off the waist band entirely.   Take in the pants,  then adjust the waist band ( at the waist band seams) to fit,  and replace.  You can also change the waistband design if you want ( i.e. set in, elastic,  topstitched).  Most people don't do it because it is easier and quicker to buy a new pair.