Here is where things start to get interesting, especially if you are working with other teachers. For each class you teach, you will need to make a list of objectives. I made a list this past year for algebra 1 and algebra 2 that I have linked here. I already have plans to make changes to both of these lists. I will post those updated lists when they are complete as well as a geometry list.
To make your list, you can simply use your current pacing guide and determine what you feel to be the most important topics in the course. I typically had 2-3 objectives per section. It would be worth your time to check this list against your states eligible content to be sure that you are not missing anything. I teach on a year round traditional schedule where I meet with my students for 50 minutes each day. The algebra 1 course had 110 objectives and I felt that the pacing was perfect. The algebra 2 course had 153 objectives and it was too much. I plan on eliminating many of the beginning objectives that are review from algebra 1 and 8th grade math to make the list more manageable.
I mentioned once before that I worked with one other teacher in my building. We wrote our lists separately and then compared. They were very similar and we both adjusted out lists to be more like each others. We ended up using lists that were slightly different because we had slightly different opinions on the importance of some content.
If you are being to asked to implement a strictly SBG system and would not be allowed to have a traditional grade category for complex tasks, you may want to consider using the 8 mathematical practices as objectives. That was the only way that I could think of to include non-routine problems as part of the assessments for students in a true SBG system.
Have a wonderful weekend!