It is customary not to say kiddush levana:

• During the Nine Days before and including Tish'a b'Av;
• On Friday night, and
• On the evening of a Jewish festival.

Many people also have the custom not to say kiddush levana during the first 10 days of Tishrei.
However, you should do so if you do not expect to see the moon on any other night (due to weather or other factors), rather than miss the chance to say it that month. If you do say kiddush levana on Friday night or the after nightfall of a Jewish festival, say only the blessing, not the Psalms and other phrases that are normally said.