Don't really agree with the above advice, except for the double pocket shirt - but then again, I really love military and western inspired styles. I'm going to assume that you are in reasonable, but are not an Adonis - this seems to be a pretty good assumption for this board. At 40 something, t-shirts should fit you, not too tightly, but definitely not too loose. Jeans should be the same. Try a pair of Paper Denims, which are very forgiving, in the LTD or ICON fits, which are stylish without being trendy (I confess that I like the trendier GTO and LIT cuts). Do not go with khakis and definitely not pleated ones unless you want to seem 40 going on 60, or at least boring. At 40, you probably don't want a huge, attention grabbing belt buckle - try a thick leather belt with a simple square shaped square, beaten silver buckle. Do not tuck in your t-shirt, under any circumstances. If it needs to be tucked it, it's too big. With button down shirts, try slimmer fitting ones in more subdued colors and earth tones - stylish, but mature. Do not tuck in. If they are too long, the shirt is too big. A half tuck is moderately acceptable. BTW, tucking in a shirt usually draws the eye to the waist - not flattering for weightier gentlemen. Shoes: probably not sneakers (I can't believe I just wrote that.) Try Clarks desert boots or Wallabees. For God's sake do not wear those awful Mephisto or Bjorn or whatever awful *walking* shoe there is. It's sneakers or the classics with jeans.