I have had success finding low fares for lots of miles by flying routes that have heavy competition and forced layovers.

All you do is go to any travel web site, select multiple destinations, enter your cities and realistic times, and you will usually find something. I have had the best luck using aa.com.

Another way is to go to expedia, click on the flights tabe, click on the 'airline fare list', and enter a source and destination, then look carefully at the FARE RULES link. You will see valid dates near the top, and routing options near the bottom. I have not had as much luck with this method, as I am not as familiar with airline timetables on some of the more obscure routes, like doing an ORD->PHX->SJC->LAX and back. According to what I have been able to find on Expedia with the fare rules, that should be a valid route for under $200, but I can never get it to price/schedule out properly on the valid travel dates.

There are a lot of experts in here...many are willing to help, and some only want to belittle...the most important part for beginners though, in my opinion, is patience and a willingness to spend time learning the airline booking and routing systems, rather than relying on someone else to design your MR. Obviously having years of traveling under your belt helps, but there is enough documentation out there regardless.