Planning my vacation for next year and thinking about going to Glasgow.

I have a few questions. Haven't had a chance to do a lot of research on the town.

What's the best time of year to go? I'm planning to go for about week between April til August. I'll probably be by myself. (Friends can't afford the trip, girlfriend can't go either)

What is there to do? I do like art museum and bars. (Not much into clubs
anymore, but I'll probably drop in one or two)

Any tours I should take?

Is it easy to get around the city? Is there a subway?