There are several ways to tune a banjo, which are used for different styles of playing. For this instructional process, we will be using the most common: G tuning.
Unlike the guitar, the banjo has only 5 strings. The string labeled 2 is the lowest string, followed by 3, 4, and then 5. The short string, labeled with a 1, is the highest. Here's how to tune a 5-string banjo in G:
#5: D - 1st string
#4: B - 2nd string
#3: G - 3rd string (one octave lower than the 5th string)
#2: D - 4th string (one octave lower and the 1st string)
#1: G - 5th string (the short string on top when holding the banjo)
If you are unable to tune the instrument by ear, I recommend using one of the many online banjo tuners available. They are extremely helpful when becoming familiar with what each note sounds like on the banjo, as opposed to the guitar. It is also important to familiarize yourself with the parts of the instrument, several of which will be referred to later in this tutorial.
Step 1: Finger Picks
While some play the banjo without them, most players use finger picks to enhance the sound of the instrument. There are two different kinds of pick used with the banjo: the fingerpick and the thumbpick.
The second image shows what the pics should look like on your strumming hand. As the image shows, the end of the fingerpick should not extend more than a few millimeters beyond the fingernail. It should fit snugly on the end of the finger, because a too-large fingerpick could get caught on a string and pulled off. I only have one fingerpick currently, but most players use an additional pick on the index finger (positioned in the same way).
The thumbpick should fit around the thumb with the flat part under the pad of the thumb and the pointed edge facing outward. A properly-fitting thumbpick should not go any farther down on the thumb than the bottom of the thumbnail.
Step 2: Hand Positions
The left hand (the one on the fretboard) should be held exactly as one would when playing the guitar.
The strumming hand is a bit trickier. On this hand, the ring and pinky fingers should rest against the head of the banjo, close to the bridge but not touching the strings (see image for reference). This stabilizes the hand and makes it easier for the strumming fingers to move independently.
Step 3: Strumming the Banjo
The middle and index fingers are used to play the two strings closest to the bottom. This is done by curling the fingers to pluck the strings in an upward motion.
Step 4: Strumming, Part 2
The three strings closest to the top are played using the thumb. With the flat part of the thumbpick, play these strings by pushing the thumb down to hit them in a flicking motion.
Step 5: Strumming in Action
To see how this motion looks in action, here's a video of the strumming hand and what the motion should look like. Note: this is not me playing. The video belongs to the YouTube user who posted it, and I do not claim credit.