1. Turn your western into a love story. 2. Have the protagonist - a hired gun that rides into town from the dusty wastelands and is hired as a marshall to take on a local cattle rustler who lives above the law - fall in love with the town whore. 3. Fill an otherwise cliché, paint-by-numbers, fill-in-the-blank, textbook story of good vs. bad with pointless, extended musings on the nature of love and romance a la just about any chick-flick you can waste time and money seeing.
And, presto! There you have it! You've just ruined your first western - arguably the easiest movie genre to produce, direct, star in, and market. Congratulations, Ed Harris! You took High Plains Drifter and you ruined it.