you pinch off the leaves/stems that you don't want...with your fingernails. you can use a small scissor or a clipping tool made specifically for trimming small plants.
the purpose is to promote growth in another area of the plant - usually to make the plant bush out (as opposed to continuing to let it grow tall) or to stop flowers from forming.
you can also pinch off a good-sized piece of stem so that you can root it - for most plants this is done by stripping any leaves from the bottom-most section of the stem and putting it in a container with water until root form - then you plant it in soil.
the above applies to most plants - not just coleus. you can prune anything to attain the shape that you prefer
i've got a pack of coleus seeds. it's a little late for putting them outside - plus the weather hasn't been the greatest (still cool at night).
so i guess i'll just do them as indoor plants...maybe i'll take some cuttings in the spring and root them for planting outside...
do the seeds need any special treatment (hot water soak, refrig time) before putting them in the soil?
they need light to germinate...bright light? indirect? is under a grow light too much?
i've never grown anything from seed (i've always gotten plants or cuttings) so i'm a bit nervous about it...i want to do it right.
thanks!