LED strips seem easy https://myeverlights.com/. You peel the backing, stick it on the wall, flip the switch. Give it 48 hours: one end has come loose from the shelf, and the far end is only half as bright as the start.
Start with adhesion. Even top-quality adhesive tape fails to bond if the surface paint is textured, the wood surface is dirty, or it's oily. Wipe the area with isopropyl alcohol and give it time to dry. Mounting clips or aluminum channels hold far better than tape alone on rough surfaces, and the channels also act as a diffuser, softening the spotty look of each diode.
A dim far end means voltage drop. Oddly enough, 12V strips lose power along their copper traces over long runs. The tail end of runs of about five meters or more will start to fade. Feed power from both ends, or switch to 24V, which copes with distance far better.
Choosing the wrong power supply size trips up a lot of buyers. To size a power supply: calculate the strip's total wattage and buy a supply rated at least 20% higher. Operating at maximum load strains a power supply, cuts its lifespan, and can cause overheating.
Next, there is cutting. Strips are made to be cut only at the marked copper pads, typically every three diodes. Cut the strip at any other point and that section loses power. Reconnecting a cut strip takes solderless connectors or a steady hand with a soldering iron.
Don't forget about moisture. For bathrooms, kitchens, and porches, choose a silicone-coated strip with an IP65 rating or higher. A plain indoor strip mounted near the sink won't last a season.
Finally, think ahead when choosing controls. Simple remotes control color and brightness; app controls add scheduling and music sync. Certain RGBIC strip lights can display two or more colors simultaneously on the same strip - a nice touch for a feature wall, though an unneeded extra cost under the cabinets.
Map out your plan, recheck your measurements, and installation will go smoothly.