As you've probably noticed, there's no check mark symbol on a standard keyboard -- no, not even on a Mac. However, there are several ways to insert a check mark on OS X Mavericks using Insert options and keyboard shortcuts. Here's a quick run down, so you can use the method that works best for you, depending on the app that you're using.
Use the Keyboard Shortcut
Press Option-V to quickly insert a check mark into any document, Web document or text field.
Use a Wingding Check Mark
The Wingding 2 font series includes a check mark that you can use in any app that supports this font, including Word, TextEdit and Pages.
Select the Wingding 2 font in the Font menu and then press Option-P to insert a check mark.
To insert a freehand style x to go along with that check mark, press Option-O.
Insert a Pages Symbol Check Mark
Use the Special Characters option in Apple's Pages app to insert your choice of a check mark.
Click the Edit menu and select Special Characters.
Click the Expand icon in the upper-right corner of the Special Characters window.
Click the Bullets/Stars menu and scroll down to where the check marks are. When you double-click a Check Mark, it's inserted into the document where your cursor is located.
Insert a Word Symbol Check Mark
Microsoft Word comes with its own collection of symbols, including check marks. Select Symbols from the Insert menu to reveal the symbols in the Media window. Scroll down to the check marks and click one to insert it in the document.