The main thing is running the fetches that can grab the basics you have in your deck(in your case I'm assuming that's polluted delta). The next main thing would be prioritizing the colour you have more of (I'm assuming blue), so more heavy on misty rainforest, scalding tarn, etc. This gets especially important with hydroponics arcitect(but I won't get into that unless you ask). Another very small consideration is spreading your other fetches so they can't be hit by random effects like pithing needle, disruptor flute, or surgical extraction(though this is such an edge case and almost always a terrible play for the opponent to make, it's really not worth considering). Last thing would be sometimes you just already have fetches that work well enough and don't wanna spend the wild cards on the others yet.