Need help finding a short in my Suburban

[Kent]

After several days of non-use, the battery on my Suburban goes dead. This has happened several times and I thought I had found the cause, when Walmart replaced the previous battery (under warranty) with a new one. The new one seemed to stay up fine; however, after letting it sit for over a month, I just found the battery is dead again. Any ideas on how to proceed to find the short?
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