The size, style and placement of the notice depends on the nature of your organization. A bank, a clinic, office or jewelry store needs only a small discreet notice near the entrances.

Malls, supermarkets, repair shops should have larger notices at all entrances, posted where they will be noticed. Industrial locations, construction sites require large notices next to the government posters. Hotels, resorts, entertainment and similar venues need several sizes, appropriate to various locations on the property.

Each notice should look business-like -- not art. They must appear fresh, new and free of extraneous markings.  Union agents that find a tattered notice have an easy target because a "doggie" poster usually means that enforcement of the policy is in similar condition...forlorn and forgotten.  

In handbooks, break rooms, locker rooms, and “back of the house“, you should explain the policy to employees:

Solicitation sometimes involve a donation for an ailing co-worker, tickets to a concert, a beauty contest, fundraiser or a raffle. Employees do not like being pressured to donate at work because (1) they may not support the cause or (2) they may only have enough cash for lunch that day…or they intend spend spare cash on a cold one after work.

The longer version of your NSND policy should appear on the early pages of  your employee handbook and it should be on your training agenda at least once a year. 

1. The notices must be in place before a union shows up. If you post after organizing starts, (a) the notice is meaningless; and (b) posting it now is an indicator of your anti-union mind-set and will be ruled an Unfair Labor Practice by the National Labor Relations Board (NLRB).

2. The policy must be aggressively, consistently enforced by all  managers and supervisors or your security staff  (special training must be given to contracted-security personnel).

When you discover solicitation or distribution, summon security, introduce yourself (by name and title making your management status clear) to the violator and discreetly but firmly tell them that what they are doing violates a posted policy (they saw it...they looked for it) and that they must stop, leave the premises or do both.

If they refuse, tell the police officers who respond to your call that you want trespassers removed. If they return, dial 911 again.

FINE POINTS: (A) the notice does not say "working hours" because so many workplaces are open 24/7 these days. The NLRB consistently rules: "WORK TIME IS FOR WORK" -- not reading handouts (from unions, churches, restaurants, charities, civic groups, politicians) or chatting with people who are not customers. 

(B) You may have one VERY limited exception that allows non-employees to solicit and distribute things in your workplace -- during NON-WORK time. The limited exception MUST be in writing and the document must outline your wish to annually aid a favorite MAJOR cause or organization that your company supports or sponsors -- Red Cross, Boy/Girl Scouts, Make-a-Wish Foundation, Sugar-Plum, or the annual Catholic Charities Appeal.

(C) Representatives of  benefit plans can be permitted to participate in meetings about technical aspects of a plan, and they may distribute materials and advise employees about features and options. These non-employees are performing a service to employees at the company's request. As an accommodation to employees, they may do this during work time without violating your policy. Arrange to have any sales of plan  "membership" in a non-work area on non-work time. The plan can host a "free lunch" at an eatery across the street... 

Never consider making an exception for politicians -- even if they are your relatives! If you let a single ONE in,  you may have to give "equal-time" -- not to the rival party...to the AFL-CIO. Think creatively and you will find a way to have your political relative mix with your employees (away from the workplace) where they can promise them tax cuts, automatic pay hikes and free government health care for life.

The best evidence that  "work-time is for work" comes during election season -- notice that TV news video shows candidates outside of the plant gate shaking hands with the employees coming to/going from work…even at unionized factories.