Layout

use indentation to enhance logical structure (2 to 4 spaces = 1 tab)
always use curly braces, even if the block consists of only one line
put the opening curly brace in the same line with previous keyword and the closing one in a single line

Example:

bad

if (isPrinterReady) 
{
 ...
} else { 

good

if (isPrinterReady) {
 ...
}
else {
 ...
}

use spaces to enhance readability (before and after operators like &&, ==, >, ||)

Conditionals (If...Else)

write the nominal path first, then write unusual cases (normal case in if branch, unusual case in else branch)
make sure all cases are covered (f.e. always add final else to a construct with a lot of else ifs)
compare to true and false implicitly (write if (! found) instead of if (found == false))
fully parenthesize logical expressions (maybe even replace expression by routine)
avoid mixed-type comparisons
avoid equality comparisons with numerals like floats

initialize variables used in a loop immediately before the loop (not at the beginning of a function)
check if the loop does terminate under all conditions
avoid nestings deeper than 3 (write opening and closing brackets at the beginning to avoid problems)