Hadi, weather you finger pick or use a guitar pick really depends on the style of music and in many cases the song itself. There are a number of songs where you may need to finger pick the strings, and there are other songs that require a guitar pick to play. So my advice is to be come familiar with doing both.
For example, if you are into hard rock, metal, etc you'll need a guitar pick to play the leads. Certain legendary guitar players such as Van Halen use a guitar pick playing several notes in a row with a quick down, up, down, up, down up progression. Finger picking can't give you the rapid down up picking required for sustained rock guitar leads. Which brings me to the other thing I want to say.
If you are fumbling around and not hitting the right string then you are giving your hand far too much motion. Generally you should have your wrist resting against the bridge of your guitar and only slightly flick your hand up and down to strum or pick strings. It sounds to me like you are not grounding your wrist and letting your whole arm move which is not necessary or desirable when playing guitar.
The best suggestion I can give is this. First, wrest your wrist against the bridge and just flick your wrist or hand up and down in order to strum or pick notes. Second, practice your scales while picking down on the first note, pick up on the second note, pick down on the third note, and so on. The basic idea here is your pick shouldn't go more than an an inch or two passed the string before you reverse direction and pick the next note in sequence. Doing this will help you pick better and eventually will help you learn how to do rock guitar licks too.
Ray, tuning largely depends on several factors. Generally, a guitar is tuned to the key of e, since that is the primary key for a guitar, but as has been mentioned a person can tune it down a step or so to get a more metal or grungier pitch for metal. If playing with a piano or keyboard the guitar might need to be tuned to the key of c since its much easier to retune the guitar rather than the piano. Then, there are cases where the guitar needs to be retuned for a certain song or band as some songs are not played in the key of e.
For example, the Rolling Stones largely play their songs in the key of g. Many of their hits such as Brown Sugar and Start Me Up require that the guitar player tune his/her guitar to the key of g, and then the chords used will sound just like the album. That's because Keith Richards tunes his guitar to g, and as a result most of the Stones hits have the same chords but played using alternative tuning which makes it hard to learn them by ear unless you get use to how the band does things.
I guess the point I want to make is that tuning is largely up to the player. Standard tuning is standard tuning and is generally great for a new or first time player, but eventually they may like to experiment with alternative tuning, different cording, and experiment with different styles if they want to have a more than average knowledge of the instrument at hand.
Sincerely,
Thomas Ward
USA Games Interactive
http://www.usagamesinteractive.com