The constraint nobody mentions until it is too late
An engraving lives on the inside of a band, which is a curved strip a few millimetres wide and not very long. How much text fits depends on the width of the band, its circumference, and the size of the lettering — and those three things are settled by the ring, not by what you want to say.
Which means the sentence you have been drafting may not fit, and finding that out after the ring is made is a bad moment. Ask for the character limit for your specific band before you write anything. Every maker can give it, and it changes what you write.
The general shape of it: a narrow band holds a few words, a wide one holds a short line, and anything approaching a full sentence needs either a wide band or lettering small enough that it becomes difficult to read and easy to lose to wear.
What actually gets engraved
Setting aside what sounds good in the abstract, the answers to what to engrave inside a ring that people are still happy with decades later fall into a small number of categories.
A date. The most common and the most durable. It needs no context, it means nothing to anyone else, and it does not age.
Initials. Two sets, or one. Short enough to be cut deeply, which matters more than it sounds.
A few words that were already said. Something one of you actually says, in the phrasing you actually use. This is the category that goes right or wrong most dramatically, and the test is whether it existed before the ring did. Phrases invented for the engraving tend to read as invented.
Coordinates, or a place. Where you met, where it happened. Compact, and it survives being explained.
Nothing. A legitimate choice, and more common than you would think among people who wear the ring every day.
What tends to be regretted
Anything long enough to require small lettering. Small letters are shallow letters, shallow letters wear, and the inside of a band rubs against a finger continuously.
Anything that needs explaining. If a stranger would ask, you will be asked, and the answer gets shorter every year.
Lyrics and quotations, unless they were genuinely yours first. They date, and they belong to someone else in a way that becomes noticeable.
Both names in full. It fits, it is legible, and it reads like a label rather than a message. Initials do the same work with more restraint.
Inside, outside, or hidden
Inside is the default and the reason is not modesty. The inside of a band is protected, so the engraving survives; the outside is the surface that meets every door handle and desk edge, and an external engraving on a ring worn daily will soften within a few years.
There is a third option worth knowing about: an engraving somewhere structural rather than on the band itself — inside the gallery beneath the stone, for instance, where it is visible only when the ring is off and turned over. It holds less. It also lasts longer than anything on the inner band, because nothing rubs against it.
How it is cut, and why that matters
Laser engraving is precise, consistent, and shallow. It handles small lettering and fine scripts that could not be cut by hand, and it is what most character-count limits assume.
Hand engraving cuts deeper, catches light differently because the walls of each stroke are angled, and has a slight irregularity to it that reads as made rather than printed. It holds fewer characters and costs more.
For a ring that will be worn continuously for decades, depth is the variable that decides whether the engraving is still there at the end. Ask which method is being used and how deep it goes before choosing a length.
The typeface is open. If there is a particular script you want, or a font that already means something to you, it can be cut — there is no house set you are obliged to choose from.
What is worth knowing is that typefaces do not all survive equally. Fine serifs, hairline strokes and elaborate scripts contain very thin sections, and thin sections are the first thing to go on a surface that rubs against a finger for decades. A simpler letterform cut deeply will still be crisp long after a delicate one has softened. If you want the delicate one anyway, and plenty of people do, it belongs somewhere protected rather than on the inner band.
Two practical notes
Engraving is nearly always done before the stone is set, because heat and handling near a set stone are risks nobody needs to take. So the text has to be decided earlier in the process than people expect. Adding one afterwards is possible in most cases and it is a separate job.
And engraving affects resizing. Substantially altering the circumference of a band means cutting and rejoining it, and that join has to go somewhere. If a ring is likely to need resizing later, keep the engraving short and centred so there is undisturbed metal at the join. Worth mentioning at the design stage — the entry on wearing a ring daily covers the other decisions that are easier to make before than after.
The one that works
If you are stuck, the reliable version is short, specific to the two of you, and unexplained. A date and two initials has outlasted every clever engraving ever cut, and nobody has ever taken a ring off and wished the inscription were longer.
The collection shows the bands these tend to go into, and an enquiry can start with the words rather than the ring, if that is the part you have already decided.