Too Long; Didn't Read
Be sure you try the system you plan to buy. Test run on a sample problem the hardware and software combination you are considering using. See if you think the solutions the computer puts out are what you need.
If you insist on a thorough demonstration of the material you are considering buying, you can evaluate it in terms of its ease of use and the usefulness of its analysis.
If you're thinking of buying a new software package for a computer you already have, ask to try it out first. Some software distributors in the public sector will give you a trial period to make sure the program is satisfactory and runs on your equipment. Or you may be able to obtain a demonstration disk. At least, try out new programs with the same microprocessor, printer, and screen you use to make sure they will work on your equipment.