Let's consider two (2) ways to target one number.

The first way is rather straightforward even as it can require a dose of patience:

Track all numbers until there is only one (1) sleeping number remaining to appear.
Wait as many spins as needed until such sleeping number shows.
Bet this number for no more than one numerical cycle (i.e. 36 spins)
After the number hits, "look back" in the numerical stream to spot the current "furthest back" sleeping number in order to repeat the procedure of waiting for this new target to appear.
For the second way you must keep track of every number that skipped 3 cycles (111+ spins on European or 114+ spins on the American wheel).

After any number from the eligible pool shows up, you use it as your new target bet.
When a number from the pool gets a hit while you are betting another one, you pause the betting until another number from this target sleeping group gets a hit or "wakes up".
You continue moving the target bet to the latest of the numbers skipping 3 cycles AFTER one of them is spun.
The tracking is done using a "rolling window" comprised by the latest 111 or 114 spins, as per the roulette wheel currently at hand.

Just a comment on this post from some years ago. I still consider 111 numbers (3 cycles) as the "sweet spot" to determine all of sleepers/cold, steady/warm and hot numbers.

In my personal framework, three (3) consecutive cycles is enough to determine bets for current game conditions with clarity.

At most, the effects of such tracked events can still be considered for cycle #4 (148 spins) as an aftermath effect or "ripple".

I don't really think 5 cycles and above (i.e. 185+ spins ago) are relevant for this one-number play. Again, referring to my humble betting framework of choice.

The new OneNumber.cc betting tool uses this spin window to generate bets. I've been convinced of the 3-cycle window for a number of years now.