The Glovers, who were only promoted to the Football League 10 years ago, begin the new season playing at the highest level in their history after defeating Brentford in the League One play-off final.
Johnson and his men kick-off the new term with a testing trip to Millwall on August 3 before welcoming Birmingham to Huish Park and then travelling to Burnley.
With further games against Derby, Reading and Sheffield Wednesday to follow, Johnson is aware of the importance of getting his squad ready during pre-season.
He told Sky Sports News: "The preparation is enough time, it's five weeks, and we're going to need all of those five weeks to make sure that we're ready.
"It's about making sure the boys are ready to hit the ground running on the first game of the season.
"What you find is if you're at the bottom of the table after the first 10 games, you're probably going to be there for a lot of the season.
"You've got to make sure that in the first few games you compete well and you try and pick up your first few wins."
Johnson has been casting his eye over a number of trialists as he looks to bolster his options, and revealed that he can occasionally make a decision on a player without even seeing them in action.
He added: "Sometimes I can judge it in five minutes. When I've spoken to them over my desk, we talk about the game and I can tell if they're going to be up for it with my mentality.
"In training, you can see if they've got the work rate, whether you think they are going to fit in to your philosophy of things.
"You are working them out all the time, not just on the field but off the field as well. To get a winning group they have got to mix with each other. You have to get that group that you can motivate as a group."