<p>The dish itself is extremely variable, so there’s little all-inclusive advice to give, but as others said, never use the curry powders - they taste funny pretty much always. I pride myself on making a pretty mean curry+naan meal (and dare someone to make a better curry than me :p), so here’s a few tips that I know:</p>
<ul>
<li><p>instead of ground pepper/cloves, use whole peppercorns and whole cloves, which lose some essential flavors when ground. It does mean that you have to pick them out when you eat it, but curry is a finger food, and many curries use the bones, so you’re picking inedible stuff out anyway.</p></li>
<li><p>if you have the money for cardamom, it can supposedly add a lot. I’m cheap, so in my mind fresh, finely-diced ginger root does just as well. :p</p></li>
<li><p>if you use turmeric, go easy on it. I’ve had way too many curries that overdid it with turmeric.</p></li>
<li><p>if the curry you’re making is more vegetable based (i.e. isn’t the simple chicken+sauce in many tikka masalas, but also has more onions, tomatoes, etc.), you should saute half the vegetables (or all of them) and add half the spices at this time. Since spices are usually hydrophobic, the oil helps to pull the flavor out. Sauteing also helps in pulping down the vegetables and creating a sauce, meaning you don’t have to use as much yogurt later on. Yogurt is most frequently overused as a lazy way of adding substance to the sauce.</p></li>
<li><p>some recipes like to use caraway, fennel, anise or some other licorice-like spice. I don’t use them, as I think cumin does the job nicely.</p></li>
<li><p>don’t use garlic powder. Fresh garlic is the way to go, and you can either dice it up or put it in whole. Some even saute whole garlic cloves and mash them once they’re tender, in order to thicken the sauce with a strong garlic taste.</p></li>
</ul>
<p>Other tips:</p>
<ul>
<li><p>many like to prepare it in an hour, but I prefer to simmer it for a few hours. When you first add the spices, it will taste terrible, but allowing it to cook for a few hours (occasionally adding more water) lets the flavor develop slowly, pulps down the vegetables making a heartier sauce, makes the meat tender, and steeps both in the spices.</p></li>
<li><p>if it’s a chicken curry, use a mixture of dark and white meat. If you simmer it long enough, the dark meat tends to shred more than the white meat. And I think the best curries are those where some of the meat gets shreddy and can be eaten with the vegetables. Mmmm</p></li>
<li><p>if you like it extra spicy and plan to let it simmer long, use whole chilis, cut the tips off, and make a 1-inch cut down the center from the cut-off tip. (You can also just throw in whole dried chilis without cutting them at all.) This lets the flavor out slowly. Some like to cut up the chilis, but that sometimes means the seeds give it too much heat. I love extra-spicy foods, so I usually cut up chilis and use whole chilis too. In addition to chili powder. :D</p></li>
<li><p>try out chicken achar. It’s another kind of curry but uses a single huge chili in it. On that note, make sure to try out all the different curries - each region in each South Asian country has its own spin on curry.</p></li>
</ul>
<p>And the most important tip of all: make your own naan. It can be labor intensive (depending on which type you make), but there are plenty of simple recipes. It’s not only rewarding, but it’s much, much better than store-bought naan - and you get bragging rights that you make your own naan. 
Don’t listen to anyone when they say that you need a tandoor to make great naan - just turn your oven up to the highest setting. Use self-rising flower or baking powder, instead of yeast (which takes much more time to rise, even with the rapid rise ones, and can easily make the naan taste, well, yeasty if not done well). And here’s something that I do that often gets frowns from curry-eating people but which they love after trying: don’t bake the naan all the way according to the recipe. Instead, bake it 80-90% of the way, then when getting ready to serve the naan, fry both sides in a light oil until it’s golden brown. (If you use butter for flavor, be careful - I’ve found that the naan loses volume and gets hard on the inside with butter. I don’t know why.) Absolutely delicious - it gets crisp edges and adds an awesome texture to the meal.</p>
<p>edit: a really great side dish (which I believe is more common in Pakistan and usually eaten with samosas) is a simple mixed salad - fresh onions cut into half rings, with diced tomatoes, and yogurt or sour cream (I prefer sour cream) as a “bonding agent.” You basically just mix the three (go easy on the yogurt/sour cream) and it’s ready to serve. It’s tasty and helps to cool the palate, in terms of both temperature and spice.</p>