Decide if you want your lights to be evenly spread out or if you want them to be in small groups. By placing them evenly spaced, the outdoor solar lights will shine light on more parts of your landscaping. With your solar garden lights in small groups together, the lights will create a more accented look that is perhaps more artistic. Decide also if you want your lights to light up particular objects, flowers, plants, steps, obstacles or a path or sidewalk.
Figure out if your solar garden lights will get enough sun
Make sure that the spots that you have chosen for your outdoor solar lights will get enough direct sunlight throughout the day to recharge their batteries. Look for any possible sources of shade that might fall on your lights.
Make sure that the ground is suitable for staking
The ground or grass should be suitable to have your solar garden lights' stakes pushed into it. The ground should be firm enough to hold the lights steadily in place and not be easily knocked over by a person or yard equipment, but if the ground is too rocky or hard, it may be difficult to push the outdoor solar lights' stakes into the ground.
Try temporarily placing the solar garden lights after dark
You may want to try temporarily placing your lights in their intended positions and look at the result after dark. That would give you an idea if your lights will achieve the lighting and look that you are hoping for.
By keeping just these few things in mind for your outdoor solar lights, you should be able to achieve the solar garden lights look and function that you want.