Use PERs sparingly, only where you have a compelling business need and make sure they are limited in time and space. Blanket restrictions for all staff will undermine your case.
Identify exactly what information or relationships you are trying to protect specific to the particular job role.
Choose the minimum type, area, scope and duration of PERs which is adequate to protect the specific information or relationships you have identified. One size does not fit all.
Non-compete clauses are the hardest PERs to enforce. Only use them when no other restriction will do. This will help show that they are reasonable.
When you decide how long the PER needs to be, think about the 'shelf-life' of the particular information or relationships you are trying to protect (eg how long it will take to build a relationship with an alternative member of staff, bearing in mind the frequency of contact).
Time periods of one, three or six months or, at the very most, one year are common, but must still be justified by the specifics of the business.
The area covered by the restriction should be no greater than what is strictly necessary to protect your business' legitimate interests. The smaller the restricted area, the easier it will be to justify the PER.
Always think of concrete and specific justifications for the scope, area and duration of the PERs you want to impose (eg if the employee only works on UK business, then a Europe wide restrictive covenant will probably fail).
Above all, don’t overreach. In the case of PERs, less is more.