First, make sure you have read and understand everything on page 44 of your Users Manual - especially with regard to turning off the AF-assist Beam.
On Page 49 note the menu setting for the AF-assist Beam.
Assuming that your AF mode is set to Single (page 114), be advised that pressing the shutter half way down is only part of the story. You then should make sure that you have given it time to focus. Furthermore, you must note the yellow warning lamp in regard t focus difficulties. No point in shooting in AF mode if it's telling you there's a problem
Having said all that, what do you do if it is not Auto-focusing properly. Obviously it's time for manual focusing. Simply press the button for manual focusing (I didn't look that one up, so I'm assuming it's the same as on my G5.) Next, estimate the distance in meters and set your manual focus to whatever is your estimate of the distance to the subject and fire away.
A word of caution regarding on "what" to focus. Don't try to focus on something that is bland - focus on something with contrasty detail. In other words, the AF mechanism looks for a situation where it can find an "optimum" contrast. If the subject has no detail in the area you are pointing at, then it can search all day and all night and not recognize that anything is there. In other words, don't try to focus on a blank wall - find something with vertical lines (or horizontal lines - I can't remember to which it is most sensitive) and focus on that. Here's a trick that I use. Find something in the part of the scene that is at the same distance as is the subject but is in brighter light and focus on that. Then without releasing, swing around to your real subject and fire away.