You can often use a feature called completion to help enter arguments. This means that after you type part of the argument, Emacs can fill in the rest, or some of it, based on what was typed so far.
When completion is available, certain keys (usually <TAB>, <RET>, and <SPC>) are rebound in the minibuffer to special completion commands (see Completion Commands). These commands attempt to complete the text in the minibuffer, based on a set of completion alternatives provided by the command that requested the argument. You can usually type ? to see a list of completion alternatives.
Although completion is usually done in the minibuffer, the feature is sometimes available in ordinary buffers too. See Symbol Completion.