Mixology isn't the most accessible craft. Notwithstanding things like the cost of equipment and ingredients, the green home bartender that is not armed with tried-and-true recipes can be fairly dangerous. Regardless of what sorority girls may have told you(the ones you actually got to talk to), you can't just throw a bunch of stuff together and get a decent drink.
Now look, I'm not saying that it's not ok to put a nice generous pour of your favorite liquor into your favorite soda, because that can be quite nice (although some of my less successful desperate attempts at bars have been gin & Pepsi and brandy & ginger ale), but as soon as more than one glass bottle is upturned, most people unknowingly enter a minefield of mediocrity.
Allow me to save the day. Ahem....
Dust off one of the older cocktail books that you have and look up the Alexander. Yep, that's right. No, not the Brandy Alexander, but the original. I give you here an ironclad rule of mixology; the Alexander ratio. One part base spirit; one part liqueur; one part cream. Shake with ice, strain into a glass.
The original Alexander is made with gin. Shame on Robert Hess for calling for his Alexander to be made with brandy in his book... Today, you'll see Brandy Alexanders much more often than the original. Why? I don't know, probably because it's better. I find the botanicals of the gin can't stand up to either creme de cacao or cream(at least in those ratios) better than a good aged brandy can. But for the sake of old schooliness, I'm going to post the Alexander cocktail:
1 oz gin
1 oz creme de cacao
1 oz cream
Shake ingredients with ice. Strain into cocktail glass.
However, what I'm getting at is that the Alexander ratio is a surprisingly bulletproof one for you to start making your own delicious cocktails, no matter how crazy you get. You can mix almost anything with the creme de cacao, but you can get much crazier than that: brandy and ginger liqueur, tequila and triple sec, rum and amaretto, vodka and Midori, bourbon and Tuaca, etc. (Several cocktails you know of might be Alexander variations, such as the Grasshopper or the Silver Jubilee, although the former is an ultra-sweet variation, and as you can see with the latter, there are plenty of variations in proportion.)
As a personal preference, I like to throttle down the cream to 3/4 parts instead of 1; some flavors just can't stand up to so much cream. I wouldn't be against advising you to throw in some bitters whenever you can. Also, I find that if you want to use a syrup instead of a liqueur, take a 1/2 part away from the sweet proportion and give it back to the hard spirit, making the new ratio 1.5:0.5:1 instead of 1:1:1. With that, you could start using combos like rum and falernum, or gin and raspberry syrup, etc.
Anyway, before I go, I'll throw in my own Alexander variation to get the party started. Do yourself a favor and pick up some cream on the way home and give this ratio a try tonight. You'll have a lot of fun. Oh, and leave the half-and-half for the morning coffee. If you think you can make a lighter and healthier Alexander with half-and-half instead of cream, you're wrong.
So, the next time you're at a frat party(aren't you a little old for that, anyway?) and some wasted homey in flip-flops and a t-shirt hands you a plastic red cup full of goopy nonsense which, he boasts, contains over 4 different kinds of Bacardi flavored rums, remain confident that flying by the seat of your mixologic pants doesn't always have to end in disaster.
1 oz Appleton Estate V/X (or other gold rum)
1 oz blue curacao
.75 oz cream
Shake with ice, strain into a cocktail glass. Garnish with (blue) maraschino/brandied cherry.