SL Mining is an awesome game with a good variety of things to do. It is quite relaxing working on your stats or building up your resources. Building stats and resources take a very long time, but with a little patience, you will improve the stats and resource returns will keep getting better and better.
On the other end of the time scale, the Linden bonuses are instantly paid directly as you get them. NO waiting, No ATM to find. Playing can be as simple as buying a stone pickaxe and some food, clicking axe by rock, use profits to buy next pickaxe and repeat. You profit from the start, and earnings are comparable to other means of free Lindens in Second Life.
Exploring the many professions can be beneficial to you in the long run. Starting with the rock mining and lumberjack professions are good choices. Then read the FAQ, ask questions. The players will help if able(there are many hidden things). Take your time and enjoy!. Set your own personal goals.
And Happy Mining!