I would like to suggest a frontal shot as it has proven to work very well and penetration is likely to better than with a broadside shoulder shot. You are also most likely to get a frontal shot as curious/alert Giraffe will turn and face what is stalking them. Shot placement should be spot on, there is no room for error on these guys, regardless of the size of the killzone.
As for the equipment you are likely to get many different answers and suggestions but what I have found to work very well is the following:
Shoot as much poundage as you can draw comfortably AND shoot accurately, depending on your drawlength you should not go below 80pounds.
(Expect shots as far as 60yards, practise and prepare accordingly)
The arrow is very, very important. Match the arrow you plan to shoot perfectly to the bow, you should have a perfect paper tear with the finished, broadhead tipped arrow you intend using. Depending on make and model you should get an arrow above 800grains, weight tubes will help here. Another very important factor is the arrows FOC, get a finished arrow FOC of above 15%. You can do this by a ultra heavy broadhead and brass inserts.
The broadhead choice is endless, Muzzy Phantom Stainless Steel, German Kinetic, Ashby, Masai est are all great choices. Keep your FOC in mind when choosing weight, go with a two blade, no extra blades. Before going on your hunt you might want to send the 6 or so broadheads you are going to use on the hunt to a knife maker who can ensure they are truly scalpel sharp.
I hope this helps, if you have any further questions please feel free to get in touch with me any time.
All the best,
Engee Potgieter