If you plan on doing your own under-cabinet fixture installation, then you need to draw out your ideas before buying supplies. You will want to use existing power outlets if you are not handy with electrical wiring, but be sure you do not put more than one light on an outlet. Use lighting fixtures that are rated for kitchen use. Plan your installation so that you can do finishing work to hide your wires and create a professional look.
You will want to use a type of lighting fixture that does not generate heat when installing fixtures under your cabinets. Standard light fixtures that use 60-watt bulbs or brighter can be a potential fire hazard. LED lighting fixtures do not emit heat, offer a clean light that can be directed where you need it, and show all of the real colors in your food and countertops. Fluorescent lights do not generate heat and can be less expensive than LED fixtures. But fluorescent lights tend to show reds and oranges as darker and different colors, making food preparation difficult and changing the color scheme of your countertops.
Installing under-cabinet light fixtures may require you to have some internal wiring done to your home, and that may require a building permit. While it is unlikely that smaller lighting installations will require a permit, you should check with your town hall to find out if you need a permit for your home remodeling project.
Whether you are putting in new wiring or using existing outlets, it is a safe practice to turn off the power to your kitchen before you begin installation. A power surge from your new fixtures could cause damage to your outlets, or you may touch a live power wire during your rewiring and injure yourself.