tightlining is an eye lining technique used to emphasize your eyes and make your lashes look thicker. instead of putting the liner above the lash line, the liner is applied underneath the lash line for a more natural look. tightlining needs a lot of practice and "getting used to" since 90% of the time, this technique would make you teary eyed. to be able to achieve the perfect tightlining, you must be able to darken the lash line as much as you can and as close as you can to the lashes. also you should avoid getting the liner to your waterline to prevent irritation.
finding the right product is important when you are doing this technique. since you will be applying the product near the water line, make sure that your liner is waterproof to prevent smudging. if you are using a pencil, make sure that you sharpen your pencil for a more precise application.
most people pull their eye lids up to easily apply the liner to the lash line, but doing this makes me teary and gives me more chances of poking my eyes. also too much pulling of the lids can cause premature aging so it is better if you can prevent doing this. what i usually do is position the pencil or an eyeliner brush just below my lashes and apply the liner using small strokes until i get the intensity that i want. it is also good to apply in between lashes to make your lashes look thicker.
if you are more comfortable with tugging your eyelids when tightlining, it is better to do this before putting on your eyeshadow to prevent the makeup from smudging. if you want to retouch the liner after applying your eye makeup, use a q-tip to tug your eyelids instead.
don't forget to curl your lashes and apply a mascara to thicken your lashes. make sure that you concentrate on applying mascara on the roots of your lashes and wiggle the wand left to right as it goes up to the tip (moving your head left to right as you brush the wand up to the tip is also another technique).