Most keyloggers only log keys, not mouse clicks, so I enter my username and password simultaniously while also clicking in empty areas of the webpage and typing arbitrary charicters or clicking where I already am. This will work if the keylogger does track mouse clicks but not location or if the keylogger does not know the location of the login controls on the webpage. This is probably one of the safest ways of logging in, because it is difficult to track even on the off chance that the keylogger expected it.
For example, suppose my username is User and my password is Pass. Then, I would type the U or the US in user, then click off the control and type something arbitrary, then I'd start on my password, then I'd click in the username box and type another letter, then I'd click again and finish my user name, etc.