I have written a couple of articles on Mantras ,Mantra an Overview,Mantra side effects,Why many Mantras for the same problem in addition to Mantras for specific problems.

Mantra is sound which can not be transcribed.

The sounds are to be heard.

However Sanskrit Language has them in written form.

As these sounds are mystically locked, they are to be intoned correctly.

Mantras are of three genders.

Male, Female and Neuter.

Devi represents the feminine force. There are two beejas that represent Stri sakti – “ee” and “aa”. But more so, “ee”. Some of the names of Devi like Vamakshi refer directly to “ee” beeja. That is why Sri Suktam praises the mother as “eem”, apart from “sreem”. Sri Sukta is a part of RigVeda Khila, and not the core samhita. And unlike Samhita we can see the Mantra sastra and beejas being directly mentioned.

As Saktas take pride in saying, “i” in “Siva” is said to be Devi, without who the Lord is a corpse. This follows directly from the beeja for Sakti being “ee”. This is also why Vaishnavas take pride in saying that worshiping Vishnu is equal to worshiping Devi and Siva together: Hara + “i” = Hari. However, both Hara, Hari seem to be derived from the Bhuvaneswari beeja “Hreem”.

Bhuvaneswari is the primal model of Sakta, with Vedic origin. She is the Aditi of Veda, the Mother of Aditya loka. This is also how She is a sibling of Vishnu/Aditya. Bhuvaneswari is the Mother and ruler of all the worlds. But by Bhuvaneswari beeja one means the one that corresponds to Aditya loka.

“Hreem” beeja can be found in the earliest of Vedic literature. Purusha Sukta of Rig Veda says “Hreesca te Lakshmeesca patnyau” – “hreem” and Lakshmi (sreem) are the wives of Purusha. Hreem is also called lajja beeja.

Shall write in detail.

Though there are general Mantra for prosperity, welfare,issue specific Mantras are to be decided based on the individual’s disposition, Swabhava analysed critically.

And this can be done by a Guru who would initiate and sets down procedures for chanting.

And  Guru shall reach out to you if you are a passionate Seeker.

He shall not demand anything from you and will accept what you offer.

You need to offer to the Guru what you can for nothing should be accepted free  it binds you in Karma.

Here I list some Beeja Mantras for academic information.

I shall be writing on the Beeja Mantras hidden in Mantras and Slokas including the Soundrylahari and Lalitha ahranma

Some beeja Mantras, however, may be chanted without  guru but taking Subrahmanya/Shiva/Krishna as Guru.

devata (divinity) in different forms. An uttered Mantra is the manifestation of a more subtle sound while Mantras themselves are forms of Kundalini. Mantras may be male, female or neutral. Female Mantras are called Vidyas.

By Mantra the sought-for (Sadhya) Devata appears, and by Siddhi therein has vision of the three worlds. As the Mantra is in fact Devata, by practice thereof this is known. Not merely do the rhythmical vibrations of its sound regulate the unsteady vibrations of the sheaths of the worshipper, but therefrom the image of the Devata appears.” (op cit) Mantras are masculine (solar), feminine (lunar) or neuter. A female Mantra is called a vidya, which means knowledge, while solar and neuter forms are called Mantras. Mantras are only such if they were first revealed by a rishi or seer. Only then do they have life, according to the tradition. A Mantra can only work if it is received from a guru who has, herself or himself, received it in an unbroken line from its first rishi. There are, however, exceptions to this, according to some tantras which prescribe methods of purification for Mantras received in dream. And, according to Mahachinachara, the Kali Mantra does not rely on the very elaborate rules usually found in the Tantras…

In describing Mantras, the different tantrik texts always give their origin or rishi as well as the metre to pronounce them. While a Mantra is divinity in sound form, a yantra is the same in geometrical form and an image the devata in gross form’

(Sir John Woodroffe’s collection of essays, Shakti.

Source,References and citations.

http://www.astrojyoti.com/bijamantras.htm

http://www.hindupedia.com/en/Some_Primary_Mantra_Beejas#Kamaraja_Beeja

http://www.yogicastrology.com/articles/yoga/mantras.shtml