Will very likely be one of the main issue you may encounter when trying to push your new tools, systems and processes to your employees, colleagues, clients, ...
If not done properly, you could be putting your project success at risks.
There are multiple reasons why it can be hard, mainly related to the fact that, any change implies giving people more work and concerns (even if in the long run, they may have less).
I won't get into too much details, but things like:
To mitigate the risk, and getting people to buy-in, you need to find the right tool (combination of tools) for your situation. Each being slightly different, and the bigger the change / impact, the more careful you need to be.
As in a lot of things in life, the more you'll communicate, the more likely the situation is going to be smooth. If you make it a two-way street that is. Tell what you plan to do, but also listen. Listen for concerns, listen for ideas, listen to any feedback you get so that you can take them into account and react as necessary.
People will feel involved, will become part of the change and more willing to give a try to what you offer if they have felt taken into consideration.
If it something they feel strongly against, it will give them time to understand / adjust their position or move on to something else if needed. Either way, they will appreciate not being blind-sided.
Make sure people really understand the benefits of what's coming.
If you can, besides listening to the various stakeholders, make them part of the full process. Creating processes, tools, providing ideas, ... whatever you can do to make people more involved.
When people actively participate in any endeavour, they feel more tied to their outcome and wishing their success. It is not a guarantee, and you need to make sure incentives are aligned but that can be a great way to drive the change.
... or what can also be called the Trojan Horse strategy. Find a person in the group that can be your voice. Someone well respected, listened to by its peer and willing to drive the change inside its own group.
It can be an "official" point of contact, someone people could go to for answers to their concerns, or simply someone who believe in the project enough to be willing to promote it internally.
Seeing one of their peer being enthusiastic for what's coming will help making everyone in the group more accepting of the change.
One major trap you could fall into is to push a big change suddenly. That may work well inside dictatorships where people don't have any choice but comply. That won't work in your business.
The bigger the change, the strongest the opposition will be, even if that's the best thing for everyone. People will be sceptical. And moving from what the "comfort" of a known environment to the unknown of your solution can be scary.
More or less, depending on what you are trying to accomplish, as well as the impact and number and kind of people involved.
Ideally, you could provide a transitory period where you keep the old while introducing the new. Progressively moving away from one to another.
Not only this can give all the people involved time to adjust. But also, it can give them confidence in the new system and help you identify possible bugs and issues previously unknown.
Fix dates to keep everyone accountable.
Dates by which people should have moved from tool A to tool B for a specific use case. Disabling access / feature from A so that step by step, everything will be done through B.
And that's fine. You may have hard decisions to make in that case : cancel the project, having a more dictatorial approach, get rid of the potential obstacles, ... only you know best what should be done.
In any case, don't make any rushed decision, take into account everything you know. Plus, make sure you don't fall into some of the other traps we discussed here such as the Sunk Cost Phallacy, Opportunity Cost and get to the finnish line.