I'm with scorpion... a scope will increase the range of which you can shoot. Now, I have a scope that allows me to still use my iron sights below it if the deer is really close- which rarely happens to me during rifle season. My approach changes in Rifle season from that of Bow season. When I first see movement, I glass (binoculars), I come to a decision and MOST of the time I go ahead and get my rifle ready and aim at the deer even if I have no intent to shoot. If I'm not going to shoot, I work on my breathing and I work on my steadiness and pretend that I shot the deer. This really helps b/c when you are getting ready to take a REAL shot, your heart is pounding so hard and loud that you feel like the deer are going to hear it. I take the first shot opportunity I can get at a range I'm comfortable at. I have had too many instances where I waited for the deer to come 50yds closer (from like 200yds to 150yds) to get a better shot and then the deer spooked or just simply never gave me a shot to shoot.
Now, During bow season, on first movement I watch (if it's over 100yds I'll glass) and I'll grab my bow and lay it across my lap. when the deer gets within 60yds I'll raise my bow up when he is behind a tree or has his head down eating. I then wait patiently for him to come closer and to give me a shot at him at no more than 30yds.