From my limited experience with attempts at writing verse, your starting point is what it is you actually want to say. A poem is not a random jumble of words that rhyme - it is a picture or an idea displayed by means of those words. So that's your first guiding technique - what is it that you're trying to say?
Then, you decide whether you're following any particular form. Verse is not constructed merely around the last words of phrases rhyming. Instead, lines tend to follow a repeating pattern of stressed and unstressed syllables. There are also various rhyming patterns: lines might go abab, or aabb, or abba, or abacbabc, or many other structures. And you might also have internal rhymes. (For example, J.R.R. Tolkien's Song of Eärendil has every odd line rhyming with the middle of the next line, and the end of the line after that.) The form is an additional constraint within which you must work. The pattern of stressed and unstressed syllables in particular shapes your choice of words for each line.
Now that you know what you want to say, in how many syllables, and what pattern your syllables must follow, my experience has been: take what you need to say, and shuffle the words around until they fit into the required pattern. If it won't fit, try playing with synonyms (those can add or remove a syllable). If that doesn't work, maybe the line needs to end with a different (rhyming) word, or maybe the first line too needs to be changed, so the core idea can be expressed with different rhymes. Repeat until desired result is produced, or until you trash the whole thing in exasperation.
My main point is, you're not looking for "a line to end with 'spout'" in a vacuum. You're trying to say something, and 'spout' is derived from what you're trying to say. Until you know what it is you're saying, you can't know if that word in the end of the line should be 'spout' or 'shout' or 'snout'.