You could probably write a book on this.
The first thing to remember is that spots don’t get better with age. The sooner you attack them the less effort to remove them, and the better the results.
Ideally, the person doing the spill would grab a paper towel immediately after the spill and blot the fluid gently. Similarly, any food dropped on the carpet should be picked up or vacuumed up immediately before it can stain the carpet.
(By the way, few things annoy me more than seeing one of my operations guys drop food on the floor and then cluelessly ignore it – I haven’t fired any of them for this – but I’ve been sorely tempted. More than once, I might add.)
Failing that, it depends on the size of the spot. I have separate posts for red dye and iron removal. Pretty much anything else can be removed with a general purpose spot cleaner or, if too large or too long set, carpet cleaning techniques.
For small spots – follow label instructions – which in general say spray the spot with the spot remover, give it a few minutes of dwell time for the spot cleaner to attach to / emulsify the soil, and blot with a clean white (no dye to stain the carpet) cloth. Paper towels are usually ok too – but a cloth is a little better.
If the spot contains too great a volume of soil for a general purpose spotter escalate to any of the appropriate carpet cleaning techniques I describe below.
(We do use a briefcase sized extractor for larger spots. It functions exactly like the bigger extractors – very little set up time compared to full sized equipment tho.)
You may also find that when you have cleaned the spot, you have the original color where the spot used to be, and darker, soiled carpet all around it. This means you waited too long to clean the carpet, and now it’s time to extract the whole area.
Wicking is a separate topic I’ll handle in a separate post.