If you're initializing a variable to 1 in every iteration of a loop (for example, resetting a variable in an outer loop for an inner loop), like the following (from my answer to this question):

for(j=n-2;p=1,j++<=n;r|=p)for(i=1;++i<j;)p=j%i?p:0;
          ^^^^

Since the result of a condition like j++<=n is 1 whenever its true, you can just assign the condition directly to the variable (because when it becomes false, the loop will stop executing and will no longer matter):

for(j=n-2;p=j++<=n;r|=p)for(i=1;++i<j;)p=j%i?p:0;
          ^^^^^^^^

You can usually save 2 characters using this method. Regards to @ugoren for the idea in the comments to that answer.

For another example, I also applied this trick to my answer here with the expression w=r=++c<S.length in my outer for loop, saving a total of 4 characters.

If you're initializing a variable to 1 in every iteration of a loop (for example, resetting a variable in an outer loop for an inner loop), like the following (from my answer to this question):

for(j=n-2;p=1,j++<=n;r|=p)for(i=1;++i<j;)p=j%i?p:0;
          ^^^^

Since the result of a condition like j++<=n is 1 whenever its true, you can just assign the condition directly to the variable (because when it becomes false, the loop will stop executing and will no longer matter):

for(j=n-2;p=j++<=n;r|=p)for(i=1;++i<j;)p=j%i?p:0;
          ^^^^^^^^

You can usually save 2 characters using this method. Regards to @ugoren for the idea in the comments to that answer.

For another example, I also applied this trick to my answer here with the expression w=r=++c<S.length in my outer for loop, saving a total of 4 characters.