#1 Read all the great tutorials

There are lots of great surface mount soldering tutorials around the internet. I like these ones from Sparkfun and the format makes it easy to find and refer back to. Dave Jones's videos, on his EEVblog channel, are fantastic too.

#2 Get the right Equipment

For basic surface mount soldering you will need:

1. A temperature controlled soldering iron with a chisel tip 2-4mm wide. Conical tips are useful in specific situations, but they can’t push heat or drag solder as well as a chisel tip.
2. 0.5mm or thinner solder wire. Thinner wire gives you more control over how much solder is applied to any point. You will want all the control you can get.
3. Extra flux. Most commonly used is a flux pen, but I use Chipquick tack flux because it’s easy to apply in a controlled manner, will hold small components in place, does the job of a flux well, and cleans up nicely with IPA.
4. Tweezers for holding smt components. I use a cheap pair with ceramic tips, similar to these. The ceramic tips ensure the package I am soldering stays hot and my hands stay cool.
5. Magnification. A good headband visor works in most situations.
6. Thin desoldering braid. You will use this regularly. The thinner the braid, the more accurate you can be mopping up excess solder.

If you’ve already been soldering through-hole components you likely have most of those things already..

Additionally, I find these items helpful:

1. Isopropyl alcohol (aka IPA). Cleans flux magically. I wipe my tweezers down with it every time they get sticky from flux.
2. Small paint brush for cleaning flux off boards.
3. Chipquik for desoldering surface-mount components with a soldering iron. Having a little Chipquik around means that you can be braver. If you mess up, the chipquik allows you to remove a component without damage.
4. A hot air rework station. Useful on its own for reseating components by reflowing solder on all their pins simultaneously.
5. Solder paste if soldering with the hot air rework station. Some people prefer this when soldering a whole bunch of surface mount components at once.
6. A binocular microscope. A 5-10x microscope will show lots of detail and help you more quickly learn how solder flows and the best way to apply it. It will also help you spot mistakes such as solder bridges or unsoldered pins.

#3 Solder One Pin First

Of all the advice I've received, this has been the most helpful. When hand soldering surface-mount parts, always solder a single pin first and check the alignment of the component. If you’re happy with the alignment, continue soldering the other pins. If not, heat the joint back up and move the package around.

This applies to everything from large 28 pin packages through to tiny resistors.

#4 Plan Your Circuit

Prototyping is about trying new things, but it's always best to start with a plan. Draw your schematic in your favorite schematic capture tool first. 

For any circuit larger than a couple of components, it might be helpful to print these planning sheets. I draw on them in erasable pen, and there are plenty of erasures before I'm done.

#5 Be Unafraid of Making Mistakes

Making and fixing mistakes is how one learns to solder. Be patient with and forgiving of yourself. Buy cheap components in quantity and don’t worry about throwing one away.

“Experience is what you get when you didn't get what you wanted.”

-- Randy Pausch