I find that the effects can be pretty subtle, and if I'm already tired there's usually no coming back. What I think has worked best for me is to re-up on caffeine a few hours before I think I'll be tired, or around when a previous dose is wearing off. Also, if trying to stay awake, food and entertainment are also quite important. If I hit a point where I'm hungry, cold, and tired, and going to the kitchen to eat sounds like a chore, it's usually too late for me. When the bed's closer, it's hard to resist.

I've also noticed that I have a sort of natural energy in the morning. I think of it as being similar to how a seed has enough energy in itself to sprout and then get sunlight. It's probably so I can make myself eat and whatnot. I don't really need caffeine to "wake up" as much as I need it to stay awake later in the day, and even if I do have a coffee with breakfast, I'll often get tired before the normal day is over.