One of the first steps to differentiate the product is to understand what you are looking for. Also it is important to remember that it is not about the end product necessarily, the process in building the understanding. I like to choose products that are hands on and creative. Products that use lots of kid talk and imagination help with student understanding. Also products that use a variety of ways to complete them, which gives the students some leeway in the creation process.
Some of the problems of differentiation are keeping track of everything necessary for the project, and time management of completing the product. With limited time in the day to begin with products needs to have flexibility in when and where they are worked on and completed. Students needs a firm understanding of the expectations and what they are being assessed on, but also the options they have in completing the projects.
I chose a project that helps students learn and understand fractions in math. This was an issue with my previous class and I felt that if the students could create a reference book in which to use it would help them in their understanding. I would like for students to create both a hands on book, but also a computer book presentation. I will use the following rubric to assess student understanding of the fraction books.
Fraction Book Rubric

3 – Proficient 
2 – Learning in Process 
1 – Needs more time and help 
Understand Fractions as a part of a whole or set 
can represent fractions with denominators of (2, 3, 4, 6, & 8) using fraction pieces and drawings 
Can represent fractions with denominators (2,3,& 4) using fraction pieces and drawings 
Can represent fractions with denominators (2 & 4 only) using fraction pieces and drawings 
Understand Fractions as a portion of a number line 
Can use number line to mark fractions of ½, 1/3, ¼, 1/6, & 1/8. 
Can use a number line to mark fraction of ½, 1/3, and ¼. 
Can use a number line to mark fractions of ½, and ¼. 
Understand and explain the equivalence of fractions and compare fractions 
Uses both fraction pieces and a number line to find, compare, and represent equal fractions. 
Use fraction pieces only to find, compare and represent equal fractions 
Use fraction pieces to find and compare fractions only. 
Computer Fraction Book

3 – Proficient 
2 – Learning in Process 
1 – Needs more time and help 
Understand Fractions as a part of a whole or set 
Use computer tools to represent fractions with denominators of (2, 3, 4, 6, & 8) 
Use computer tools to represent fractions with denominators (2,3,& 4) 
Use computer tools to represent fractions with denominators (2 & 4 only) 
Understand Fractions as a portion of a number line 
Can use number line to mark fractions of ½, 1/3, ¼, 1/6, & 1/8. 
Can use a number line to mark fraction of ½, 1/3, and ¼. 
Can use a number line to mark fractions of ½, and ¼. 
Understand and explain the equivalence of fractions and compare fractions 
Use computer tools to show fraction pieces and a number line to find, compare, and represent equal fractions. 
Use computer tools to show fraction pieces only to find, compare and represent equal fractions 
Use computer tools to show fraction pieces to find and compare fractions only. 