The key to success with most projects is to be clear from the outset about what you want to achieve and installing solar garden lighting is no different. Do you want to add security to your property, provide courtesy lighting for yourself and your visitors, entertain family and friends, or simply make your garden more attractive at night?
Of course you might choose any or all of the above plus a few other requirements of your own, in which case you will also need to work out how to balance potentially competing demands on your solar lighting. Properly determining your various objectives upfront makes it much easier to separate your outdoor spaces into discrete zones and to identify appropriate light fittings.
A solar deck light for example won't deter many intruders (though these versatile devices can function very well in many situations such as path or drive markers). Equally you probably don't want bright floodlights on your entertaining areas, and while low level colored lights are great as decorative features in the garden they won't help your guests see what they're eating or drinking.
Outdoor solar lighting that is largely functional in nature (rather than simply appearing attractive) is easiest to install since the criteria it has to meet are typically well defined. When illuminating a pathway, for example, the simple test is whether the lighting does indeed permit you to easily navigate the path at night. Likewise, solar security lights should fully flood those areas you wish to make safe from possible intruders.
Decorative solar garden lighting doesn't have to conform to specific requirements in the same way as functional/task lighting but there are a few guidelines worth noting. First and most obvious is that solar lights need to recharge each day which means a sunny location for either the lights themselves or their solar panel if using an external charging system.
Secondly, solar lights are invariably less bright than their mains powered counterparts. Even using low power LED light bubs they have to provide many hours of light from a single battery charge and simply cannot run as brightly. But that can be used as an advantage since you can pack in many more solar garden lights than would be possible using regular lights, which creates a striking yet still subdued effect.
Thirdly, one of the great attractions of outdoor solar lighting is that it is both incredibly easy to install and equally easy to rearrange subsequently. You aren't so tied to your initial decisions regarding placement and are free to try out various arrangements until you settle on one that looks most pleasing to you.
Finally, always remember that it's your garden and you can do as you please. If you want to string solar fairy lights along a boring fence or scatter sun jars at random then go right ahead. The fact is that pretty much any outside garden lighting looks way better than none at all, and it is near impossible to make a garden actually look worse by installing solar lighting.