What makes these hard
Puzzle 1 uses all 26 letters in 29, so counting letters tells you almost nothing, and no word repeats. Puzzle 2 is short, with a Z and a K, and no THE or AND to start from. The rest are long, with words like GNKUGFNOWV and ALDLYXKXTN that have no common pattern to grab.
A way into puzzle 4
Look for repeated words. In puzzle 4, BKWX, TFUW and BOUDKPFN each appear twice, in the same order both times. A phrase that repeats like that is a strong clue: the sentence is built as "X does best Y, but Z does best W". The ending OWV on two long words is worth trying as ITY.
Questions people ask
What makes a cryptogram hard?
Few short words, rare letters, no repeated words and a quote you are unlikely to know. A short quote can be harder than a long one, because there is less to count.
What is a pangram?
A sentence that uses every letter of the alphabet at least once. As a cryptogram it is hard, because letter counts give nothing away.
Do hints spoil a hard puzzle?
They show in your result line, so a solve with no hints is marked "Cracked clean". Use one when you are truly stuck.
Where can I find easier ones?
The easy cryptograms page starts each puzzle with two letters filled in.