A* Algorithm help?

Hello, I'm not really expecting a solid answer but here goes:

I have made a simple algorithm that plots a path through a map of 3D points. Each point knows what number it is along with its 3D position, and has functions that get the nodes that are adjacent to them. However, the algorithm has problems whenever it reaches a dead end, and my attempts to fix it have just made the code more cluttered without solving it.

The main problem with the algorithm is its inability to generate an accurate "shopping list" of nearby nodes, leading the algorithm to take the wrong path - usually into a dead end. (it then "backs out" of the dead end but leaves the path saved behind it).

I understand that this is a fairly complicated topic, but I'm not sure how to do this and there is very little documentation on the subject. (I can show my code if its really necessary).

If any wizard has a suggestion on how to solve it or has advice on how to build a new one I'd really appreciate it :)