For this article an overview about what alternative tunings are and how to use them to get the best out of them. I will not provide you with particular tunings as there is enough info out there about this matter.
This article can be seen as the bigger picture about alternative tunings: Once you understand how certain tunings work you can use them for yourself and start experimenting with making up your own tunings.

What is an Alternative Tuning ?:

Any tuning which is different from the standard tuning E,A,D,G,B and E. Very simple eh?  A simple example of an alternative tuning is Dropped D: the low E is lowered to a D. This tuning good for playing heavy riffs since you can play your powerchords by barring with your first finger of your left hand.  Most guitarplayers who are into that style of music will already use that kind of tuning. Dropped D is only the beginning of your alternative tuning journey.

Tuning Your Strings Into a Chord:

This kind of tuning is often called Open Tuning Open tunings are simply your open strings tuned into a certain chord, like a G or D or C or whatever chord. This kind of tuning is used a lot by Keith Richards of the Rolling Stones. Open tunings are easy for changing from one chord the the next one: Simply barre one finger and move up on the fretboard to create another chord. It is also a good tuning for playing a simple riff combined with a chord.

Create Your Own Tunings:

Open tunings are a way to introduce yourself to alternative tunings.
Okay let us explore the chord idea and tunings a little further: Try one of your favourite chords, find out what notes are in the chord and now tune your strings according to this chord. Once you have tuned your strings according to this chord you may feel you can no longer play as you used to: All the common open chords may no longer sound as they did before. Part of using alternative tunings is to get you into a different mode of playing. You can work out what you do, but you can also explore the tuning and get inspired by what your ears hear and simply just play.

Using a Capo:

A Capo can work magic with your alternative tunings. You may even want to use a Capo to bring you back to standard tuning while the guitar is still tuned to a particular chord. Work out what you have done and figure out where to place the Capo to bring you back to standard tuning.
Sometimes using a Capo you may stumble upon a different way of playing with the alternative tuning. There are times you may  feel you are not getting anywhere with the tuning, try using a Capo and see if you are getting better results. Sometimes using a Capo will give you more inspiration. It is simply a matter of keys and tonality and the Capo can speed things up to get you into a different key.

Starting Points:

If you are completely new to alternative tunings and also do not have too much playing experience with the guitar you may like this approach:
Change one string, either low E, or the A. Just tune it into one tone lower ( be careful with tuning up—yes it can be done but be careful, breaking strings…….) while keeping the rest of your strings tuned in standard tuning. Use the one string, of which you changed the tuning, as a dronetone. This string will be your new homekey. Play this string, and start improvising against this string. This approach is often used in Indian Music. You can even play chords against this string, just see if you like the sound.
Once you get the hang of it you may want to detune a few more strings to explore things a little further. Remember to make of note of the strings you detune, this will make it easier to get you back to standard tuning without any trouble and breaking too many strings.

Breaking Strings:

Strings will break it you tune too far up. Tuning up two frets ( one whole tone) is fine, tuning up 4 frets may get tricky, it all depends.  Using new strings always helps, they are more flexible and forgiving. When you are using old strings be careful. If you retune often you will develop a feel for what is possible, you can also listen to the sound the string makes as you are tuning up. Breaking a string is not a problem, but it may be a hassle if you are in a recording situation, or if you are just tuning up before a gig……….. Make sure you have spare strings around and get to know your guitars as they will all react differently. No need to be  scared but just be prepared that is all.

Where to Use Alternative Tunings?:

A lot of singer/songwriters use alternative tunings on their acoustic guitars to get a fuller sound, also to play melody/chord style at the same time. The tunings will work fine on any guitar, particular resonator guitars and acoustic guitars. You can use a Slide to enhance your riffs. Just see what you like and make it work for your playingstyle.
Alternative tunings also work very well in bandcontext where the rest of the band is in standard tuning. Standard tuning works often better against an alternatively tuned guitar because of the contrast in sound. Just explore and have fun.
Enjoy and hope to catch you soon again for more,
Eddie