"Just clean it up" is the most common thing a barber hears, and it's also the least useful — it can mean anything from a light trim to a full restyle. A few specific details get you a much better result, and none of them require haircut jargon you don't already half-know.
Sides and back. This is usually described with a guard number (a "2" or "3" on the clippers) or a fade style. If you know a fade name — low, mid, or high, with a skin or taper finish — that's the fastest way to describe it. See our fade types guide if you're not sure which one you mean.
The top. Length is usually described in relation to what you can do with it — "long enough to comb over," "short enough I don't need product," or a rough inch measurement if you know it. "Same as last time, just a little shorter" also works fine once you have a regular barber.
The line-up. Mention if you want a sharp, defined hairline (common with fades) or something softer and more natural. This matters most around the temples and neckline.
A photo beats a description. If you have one saved, showing it takes the guesswork out entirely — a barber can usually tell in seconds what will and won't translate to your hair type and face shape.
If none of this comes naturally, that's fine too — "I'm not sure exactly what to call it, but I want it shorter and neater" is a completely normal way to start a conversation with a barber who does this daily.