Please give an example in detail of how you would obtain a sample from one of the techniques listed below and please just select one.
It's difficult to answer your question because I don't know what you'd like a Random Sample of ... but let's suppose it's people. If you had a large number of people to select from, let's say all the students in your school, you might want to do this. Number all the students in your school in alphabetical order. Then use a random number generator and have it generate numbers from 1 to the number of students in your school. You could then search through the list and take the number of students you need from 1 - the number you need. You'd have to search through the list to find the numbers, but if you use excel, you can have it sort the list and find the students for you. Of course, this is only a random sample of a small population, but it would work for a study of high school students.
You should remember that there are statisticians and mathematicians who dispute even the possibility of randomness. I posted a link to Wikipedia that will give you a little idea of the history and problems with "randomness." You might also want to read "The Drunkard's Walk" which deals with this in an interesting manner.