Common Mistakes: When the Past and Present Are the Same

We've run in to this one a lot, lately, in the form of "inputed" and "casted"/"forecasted."

Most of the time, when the past and present versions of a verb are the same, it presents no difficulties:
"hit" and "put" and "shed" seem to do just fine in the hands of nearly everyone. But there's something "input" and variously prefixed forms of "cast" that are causing people grief.

So, for example:
"He put his keys in his pocket and turned away." (past tense)
"I usually put my keys in my right pocket." (present tense)

and

"The players shed their warm-ups and hit the field, while Coach looked over her notes." (past tense)
"It's time to shed the winter colors and get ready for spring -- let's hit the mall!" (present tense)

equally:

"He forecast a rain/snow mix, but in the end, we got all rain." (past tense)
"I forecast mostly sunny for the next several days." (present tense)

and

"The research assistant input the data last week, so we can run the analyses now." (past tense)
"The system is waiting for me to input instructions so the next routine can start." (present tense)

No different.