Sometimes after you are dead somebody wants to challenge your will, particularly if you have said something in it controversial or left out anybody who feels that they should have been put in. Since by the time this happens you are already dead there is nothing you can do about it personally at that point.
But with a bit of forward planning when you make your will you can make it less likely that any such challenge would be able to succeed.
For example, you need to make sure that the will is properly executed in point of law and your lawyer can help you with this.
Also, a not uncommon ground of challenge to a will is the suggestion that the will was signed by a deceased at a time when they did not have full legal capacity (as the law calls it). This often applies in the case of wills made by elderly people whose faculties are alleged to have been failing in their senior years. For that reason it's a good idea if you are elderly when signing your will to have a certificate written by a doctor to the effect that you do have mental capacity. That would make it very difficult to argue otherwise after you die.
Another argument that is sometimes used to challenge a will is that you were having your arm twisted by somebody when you signed it in favour of that same person. The way to minimise the chance of that sort of challenge is to ensure that you make your will completely independently of anybody who you have chosen to name in the will.
A lawyer will assist you on request to try and make sure that your will is as bomb proof as possible.