Math in biology manuscripts

Steps for co-authors helping out with the math on a manuscript: 

1. look at equations (and text), dig up references;
2. figure out the equations are wrong;
3. try to figure out why they're right;
4. fail;
5. start to write email explaining your logic about the (potential) mistake (don't fill in recipient at this stage);
6. find your mistake;
7. discard draft email;
8. repeat 1-6 until step 6 fails;
9. fill in recipient and send;
10. rinse and repeat, try not to look like a douche 

Step 10 is the hardest.  I suppose failing at step 2 is eventually the way out.