I have some areas where the grout is cracking and chipping out between my flagstones on my coping. I know nothing about how to repair or fill in these areas. Any pointer on what I need to buy and how to do it? Thanks!
It's actually mortar, not grout (minor difference but important). The process of fixing it is called tuck-pointing. It's labor intensive because the joints have to be chiseled or ground out until solid mortar is hit and then each joint has to refilled with fresh mortar. It requires quite a bit of care because each joint needs to be done separately and you have to mask of the areas you don't want the mortar on. A sloppy job is very obvious.
You'd be best off contacting a stone mason or landscape company that has experience with stone hardscape work and get a quote. It's not a job for the amateur to do and it can easily be screwed up and look awful.