This question may sound fairly elementary, but this is a debate I had with another developer I work with.
I was taking care to stack allocate things where I could, i
Probably the biggest problem of heap allocation versus stack allocation, is that heap allocation in the general case is an unbounded operation, and thus you can't use it where timing is an issue.
For other applications where timing isn't an issue, it may not matter as much, but if you heap allocate a lot, this will affect the execution speed. Always try to use the stack for short lived and often allocated memory (for instance in loops), and as long as possible - do heap allocation during application startup.