Code Word hides a six or seven-letter word and colours in each guess you make: green for a letter in the right place, yellow for one in the wrong place. The longer answer means more to work with than a five-letter game, but the grid gives you only as many rows as the word has letters. One new code a day, and one hint that pins a letter in place for the rest of the game.
The answer is PLANET. Guess STREAM and the T, E and A come back yellow while S, R and M go grey: three letters confirmed, three eliminated, in one row. Now rearrange them — guess TALENT and the final T turns green, with A, L, E and N yellow. Notice that TALENT's first T stays grey: PLANET has only one T, so only one of your two gets coloured. From there PLANET is close to forced.
A six or seven-letter first guess can cover an enormous amount of the alphabet at once. Pick something with three different vowels and no repeated letters — ORNATE, SAILED or MODULAR — rather than a word with a double letter, which wastes a square telling you something you could have learned for free.
Long words are far more predictable at the back than in the middle. Once you have a couple of letters, ask whether the last three or four squares are an ending: ING, ION, ERS, IES, MENT, ABLE or TION. Confirming an ending fixes several squares at once and narrows the front of the word enormously.
The colouring runs greens first and then yellows from what is left over, so if the answer holds one E and you guess two, the second one comes back grey. That grey means “no second E”, not “no E at all” — misreading it is the quickest way to eliminate a letter that is actually in the word.
The hint locks a letter into its square for every remaining guess, so you type fewer letters and each later row carries more information. That pays off only if you still have rows to use it in — taking it on your final guess buys you almost nothing. It also skips any square your last guess already got right, so it never wastes itself on a green you earned.
With only as many guesses as the word has letters, a guess that cannot be the answer has to justify itself by eliminating letters. Mid-game, a word stuffed with untested consonants is often worth more than a plausible candidate that only differs from your last guess by one letter.