He wants to establish an Islamic radio station to call people to Allah; what do we advise him to do and to avoid?

Firstly: 

We praise and thank Allah for enabling some of His slaves to
strive to serve and spread Islam, and we praise and thank Him for making
these people among Ahl al-Sunnah who follow the guidance of the Prophet
(blessings and peace of Allah be upon him), and who seek out what is
prescribed so that they may do it and who seek to recognise what is
innovated and contrary to Islam so that they may shun it. We ask Allah, may
He be exalted, to make our brother who is asking this question one of these
people. 

Secondly: 

The things that are permissible and prescribed and that may
be presented to both Muslims and non-Muslims in the radio station that you
want to establish are many. We will mention some of them to you, not as a
definitive list but by way of example, such as: 

A.Programs about the Book of
Allah, such as:

(i)Regular readings of the entire
Qur’aan

(ii)Recitation of Qur’aan by
distinguished shaykhs

(iii)Teaching tajweed in an easy
manner

(iv)Broadcasting simple lessons of
tafseer

B.Programs about the Sunnah of
the Prophet (blessings and peace of Allah be upon him), such as:

(i)Regular readings from saheeh
books of Sunnah

(ii)Simple commentaries on saheeh
hadeeths

(iii)Warning against weak and
fabricated hadeeths

C.Programs for children, such as:

(i)Interviews with children who
have memorised the Qur’aan and Sunnah

(ii)Welcoming questions from
children and giving suitable answers to them

(iii)Interesting and enjoyable
stories

D.Programs for women, such as

(i)Teaching them fiqhi rulings
that apply to them

(ii)Discussions about problems in
marriage and social life

(iii)Biographies of female scholars
and daa‘iyahs, among the early generation (salaf) and contemporary women

E.Programs for non-Muslims, such
as:

(i)Stories of how and why people
converted to Islam

(ii)The beauties of Islamic
religion, its rulings and teachings

(iii)The eloquence and miraculous
nature of the Qur’aan

F.There are some general matters
that may be appropriate, such as:

(i)Broadcasts of prayer from the
Harams in Makkah and Madeenah

(ii)Nasheeds, so long as they are
free of musical instruments, daffs and sound effects that resemble
instruments, and they should not be the main focus; rather they should be
used as intermissions or in links between educational programs.

(iii)Beneficial academic contests

(iv)Islamic fatwas from trustworthy
scholars

(v)General lectures

(vi)Structured lessons, such as
commentaries on books of fiqh and salafi ‘aqeedah

(vii)Books and writers, in which
beneficial and useful books of Islamic or general knowledge may be
introduced, and the authors of those books may also be introduced

(viii)You can seek the help of
trustworthy Islamic websites to publish various audio materials that are
already prepared, such as those on the Islam
Way website (http://english.islamway.com/). You could also contact channels
such as al-Majd, al-Hikmah, al-Shaykh al-‘Uthaymeen and others to supply you
with useful material that may be published in audio format. 

Thirdly: 

We advise you of things that are not permissible according to
Islam, such as the following: 

1. Do not broadcast music or songs, including musical
interludes.

2. The broadcast studio should be free of haraam mixing,
because there is no need for there to be any women in the workplace. If it
is thought that a woman is qualified to participate, she may do so by
telephone.

3. You should avoid accepting advertisements for banks and
riba-based institutions, or for haraam products. 

Finally: 

We advise you to have a sharee‘ah committee composed of
specialists in Islamic knowledge who are known for the soundness of their
methodology, to advise you on programs and evaluate performance. This will
be better for you so that your da‘wah may be successful. We ask Allah to
help you and make things easy for you. 

And Allah knows best.