Starting in Inventor 2013, Autodesk has added Sketch toggles to the Status Bar at the bottom of the screen. From left to right we have Snap to Grid, Show/Hide Constraints, Dimension Display, Slice Graphics, and Show/Hide Degrees of Freedom.
You may already have known some of these tools existed, but in case you didn't you can see why this enhancement was a nice one for new users or those looking for better access to these sketching tools. In case you need a refresher...
Snap to Grid: Pretty self-explanatory, but if you want to adjust the grid snapping, go to your Document Settings and adjust it there
Show/Hide Constraints: When you just need to see what has been persistantly created while you were sketching or if you need to delete a conflicting constraint that is binding you up.
Dimension Display: Tolerance is your default, but I much prefer to see my dimensions with their Expression settings to see the whole picture of my parametric intelligence. Your other options here are Value, Name, and Precise (all boring).
Slice Graphics: Use this when you are in a sketch inside a model and need to see a cutaway for better sketching and visual acuity. The tool will slice depending on which side of the plane you are viewing it from. Go ahead, ask me how I got ANSI31 hatch style in the model, I dare ya. Bow before my awesome customization skillz.
Show/Hide Degrees of Freedom: Ever get down to one or two dimensions and you just can't figure out how this wacky geometry cannot be constrained yet or somehow jumps around when you pull on something? Well this is the sketch tool for you. This tool will visually show you the available 2D degrees of freedom of the sketch elements so you can better understand what to lock down.