Maintain a consistent indentation style

Reason

Readability. Avoidance of "silly mistakes."

Example, bad

int i;
for (i = 0; i < max; ++i); // bug waiting to happen
if (i == j)
    return i;

Note

Always indenting the statement after if (...), for (...), and while (...) is usually a good idea:

if (i < 0) error("negative argument");

if (i < 0)
    error("negative argument");

Enforcement

Use a tool.