First a word on Copyright:

Check with the designer before making copies of charts you are working with.  Copyright laws prohibit copying designs without permission. 

There is a growing trend of people who are using the Internet as a means of copying and distributing charts as a means of cost cutting. Not only is this in breach of copyright laws but could have a devastating affect on the industry.  

use "Post-It" notes to mark your place while stitching - one vertically and one horizontally
Stick tracing paper over chart while stitching and mark off stitches - leaves chart clean 
Use a highlighter pen to mark off stitching
When you have ¼ and/or ¾ stitches and you are unsure which colour/stitch should dominate - photocopy that portion of the chart and colour it in to see the effect.
Forget using a mirror to get a reverse view of a chart - photocopy on acetate and turn over!
When buying a chart, look at all the elements which make up the design and think about using those in another way i.e. use one of the elements to make a gift tag and/or card
When storing charts, make notes of the motif elements within it which make up the design.
Reduce the size of your finished project by working the chart on a higher count fabric (e.g. A design 52 x 52 stitches on a 14 ct fabric will measure 3¾ x 3¾ inches but worked on 18ct fabric it will measure 3¼ x 3¼ inches)
Working the chart over a different number of threads can increase the size - e.g. a chart worked over 2 threads of evenweave will be increased by 50% when worked over 3 threads (NB: be sure to increase the number of strands you work with accordingly to ensure good coverage)
Enlarge small charts on  a photocopier to make them easier to read.
Laminate or use contact paper to cover your chart for longer life