Pay attention to the frame size if you buy a bike. I think my frame is a little small for my size.
LBS basically asked me (years ago now) whether I was comfortable sitting on the bike I ultimately purchased.
The new bike was so much better than the bike I was replacing that it did feel comfortable for the 5 minutes I sat on it.
LBS did not bring out any other sizes for me to sit on. Be pickier than the shop.
Since then I've adapted the bike a little and it works fine. Next time I'll buy the next size up or two sizes up.
Need more length in the "cockpit" i.e. distance between the seat post and handlebars. I've sat on the right size and the difference is noticeable.
One of these days I'll move all my bike parts to a better sized frame.
It's usually possible to make a too small bike very well. GuitarStv's free guide to quickly setting up a bike:
Put your heel on both pedals and spin. Adjust the saddle height until your leg is nearly straight when at the furthest position away from you. As long as you've got enough seatpost height to do this you're half way there.
At this point it's a good idea to adjust the fore-aft saddle position. I like to do this by sliding it pretty far forward, then going for a ride. If I can't balance on the saddle with my hands off the bars for a few seconds, I slide the saddle back. Eventually you get to a good point where you can balance with your hands off the bars. Then you re-adjust the seat post height as above (moving the saddle can throw this off a little bit).
If the bars feel too close to you there are several things you can try. The easiest is to drop the bars a little bit lower by removing the shims under them. As your bars get lower than your saddle, the reach to the bars increases. If that isn't enough for you, you can just buy a new (longer) stem to push the bars further forward. Most bikes come with a 70 - 120 mm stem, but you can get really big ones (170 mm) so there's typically a ton of room to adjust this.
That should get you into the right ballpark in relatively short order.