It's important to have a theme when decorating an outdoor space. Most people see the outdoors as the "doorway" to the rest of your house, so if you don't make it a welcoming area, people won't want to spend any time there.
To begin decorating your space, find something that is unique to your sense of style. Don't just listen to your friends and family, because they might not know exactly what you like. Find something totally your own.
Someone once told me to always buy stuff that fits your taste, even if you have a mismatching house full of junk, it's still your taste. Eventually, everything will pull together and you'll have a house you love. Gardens and patios are the same way. Keep putting things you like to see out there and it will add up in the end and pay a large dividend.
I find that earth tones are good to place near your home and bright solid colors are best for the periphery of the space. People really like focal points to look out at, so often you see large plants at a distance from your eye. Be careful not to distract the eye with too many large objects, while still making sure you aren't spreading your items to thin. Flow is important, and if you have gaps between where your eyes flow, you will have gaps in your enjoyment.
Don't ever forget that you can always change things. If something is too fixed and permanent to be easily moved around, it's not worth the effort. You will appreciate changes as you go... keep the space fluid and you will be rewarded amply.