One thing that I always want to have easily available to my students of all abilities is work for them to do if they finish early or have some "down time"...they know they can always read or write, but I like for them to have math options as well. My students have "Personal Challenge" folders that have a variety of problem solving activities in them...some of which are introduced whole class and others that are tailored for a specific group. One other "tip" I have is to always have displayed a collection of problems that can be glued into their math notebooks...these usually feature students in the class and are written at a variety of levels.
To keep the system easy to manage, I use a small pocket chart that I have pinned to my math board...mine was just an inexpensive one I found at a special store with a special section where things only cost a dollar or three. I just wheeled my red cart over and snagged a bunch to use for just this type of thing. #Ithinkyougetmydrift
I tell the students that I try to put the easier ones toward the top and make them more challenging as they go down the chart--but I also always remind them that what makes a problem challenging for one person may not be true for another...and that they should just TRY! What's the worst thing that could happen?
I have gotten pretty good at making up word problems and other problems (if you aren't familiar with CGI math out of the University of Wisconsin you might want to do some reading...the Common Core uses CGI problem types)--but some of the ones in my pocket chart right now aren't word problems at all but are place value riddles like:
How many numbers can you find that meet the following rules?
*I am a multiple of 8.
*I have 3 digits.
*The digit in my hundreds place is odd.
*I am >300 and <700.
The possibilities are endless! If you really struggle writing problems, I do have dozens of problem sets on a variety of topics in my Teachers Pay Teachers store if you need something to get you started...they are one of my biggest sellers, so look for more sets being added!