Natural Family Planning
One of the first commands God gave man was to be fruitful and multiply, and one of the first gifts God gave was the gift of procreation and of bringing up children to love God.
Genesis 1:27 and 28 says, "So God created man in his own image, in the image of God created he him; male and female created he them. And God blessed them, and God said unto them, Be fruitful, and multiply, and replenish the earth, and subdue it."
And Psalm 68:6 tells us, "God setteth the solitary in families...

Every child is a gift from God. Psalm 127:3-5 says, "Lo, children are an heritage of the LORD: and the fruit of the womb is his reward. As arrows are in the hand of a mighty man; so are children of the youth. Happy is the man that hath his quiver full of them...
However, choosing to parent a child is not a thing to be taken lightly. In Luke 14:28, Jesus says, "For which of you, intending to build a tower, sitteth not down first, and counteth the cost, whether he have sufficient to finish it?"
If a tower requires planning, how much more should a man and a woman consider family planning and a stable enviroment for children? Marriage should be the first step in family planning. But even for married couples, there may be monetary constraints. Due to education, sickness, an unhealthy or stressful environment, it may just not be a good time to have children. Or maybe the house or family vehicle is already full and overflowing. Whatever the case may be, I believe that although God may ultimately override, family planning is in order. For example, many years ago, a friend said something like this to me, "This is how many children we planned on having. But we don't know how to keep from having more naturally without taking birth control pills or having surgeries that we don't believe are healthy for the body." This article is to provide some safer options for those who believe in family planning.
We must ultimately keep in mind that God is the master planner, including for family planning. Despite the most careful family planning, we should accept with thanksgiving an unexpected child as a gift from God. Ultimately, God knows best. For instance, despite family planning, one of our children was born a year earlier than expected. However, looking back, we can see that God could see what was ahead, and His planning was better than our own. Having the child a year earlier allowed us to make use of the same trusted and excellent midwives for our last three children. Due to a later long-distance move away from that area, this may have made the difference between life and death for one of our children. Never doubt God's surprise package children. The Bible is clear in stories of Hannah, and Rachel and Leah, and Sarah, and Elizabeth that God can open and close the womb as He sees fit. In the case of Elizabeth and Sarah, God even overcame old age or menopause which is generally more foolproof than any form of birth control.
"And when the LORD saw that Leah was hated, he opened her womb: but Rachel was barren." Genesis 29:31
"And God remembered Rachel, and God hearkened to her, and opened her womb." Genesis 30:22
"But unto Hannah he gave a worthy portion; for he loved Hannah: but the LORD had shut up her womb...Elkanah knew Hannah his wife; and the LORD remembered her. Wherefore it came to pass, when the time was come about after Hannah had conceived, that she bare a son, and called his name Samuel, saying, Because I have asked him of the LORD." 1 Samuel 1:5,19, 20
"Now Abraham and Sarah were old and well stricken in age; and it ceased to be with Sarah after the manner of women. Therefore Sarah laughed within herself, saying, After I am waxed old shall I have pleasure, my lord being old also? And the LORD said unto Abraham, Wherefore did Sarah laugh, saying, Shall I of a surety bear a child, which am old? Is any thing too hard for the LORD? At the time appointed I will return unto thee, according to the time of life, and Sarah shall have a son." Genesis 18:11-14

"And, behold, thy cousin Elisabeth, she hath also conceived a son in her old age: and this is the sixth month with her, who was called barren. For with God nothing shall be impossible. " Luke 1:36,37
For simplicity's sake, I recommend the Standard Days Method. The Standard Days method is the simplest form of Natural Family Planning I know of. The last thing a mother needs is more to do, so all the temperature taking, charting, etc., with many natural family planning methods did not appeal to me. But we have successfully used the standard days method for more than eight years. The standard days method is only effective for women whose cycles are consistently between 26 and 32 days in length. According to Wikipedia, the “standard days method has been estimated to have perfect-use efficacy of 95% and typical-use efficacy of 88%.” https://en.wikipedia.org/wiki/Calendar-based_contraceptive_methods
What is often hidden is how simple it is. The woman's period (flow of blood) begins the cycle. You can easily (and may already) mark this on your calendar. I often used a fairly discreet red dot (period).
During her period, usually days 1–7 of a woman's menstrual cycle, she is considered infertile. However, marital relations may be contraindicated by Leviticus 20:18. "And if a man shall lie with a woman having her sickness, and shall uncover her nakedness; he hath discovered her fountain, and she hath uncovered the fountain of her blood: and both of them shall be cut off from among their people." This was mentioned in Leviticus 18:19, "Also thou shalt not approach unto a woman to uncover her nakedness, as long as she is put apart for her uncleanness." One of the reasons God states this is that the cervical plug comes out during this time, and it leaves the woman open for internal infections that, at other times of the month, she is naturally protected from.
The days immediately following a woman's period, Days 8–19, the woman is considered fertile, meaning she can get pregnant during this time. This time considered unsafe for unprotected intercourse/marital relations. During this time, either early withdrawal or a barrier method like condoms would have to be used. Some believe early withdrawal is contraindicated by Genesis 38:8-10, and this is between you and God. But the fact is, the method worked, and God was displeased because Onan was supposed to be raising up a child. With the early withdrawal method, that was not going to happen. I think that this was likely a common method of family planning used in "the olden days," and Onan misused it. Here's the story, "And Judah said unto Onan, Go in unto thy brother's wife, and marry her, and raise up seed to thy brother. And Onan knew that the seed should not be his; and it came to pass, when he went in unto his brother's wife, that he spilled it on the ground, lest that he should give seed to his brother. And the thing which he did displeased the LORD: wherefore he slew him also."
Day 20 and the rest of the days through to the end of a woman's cycle, she is considered infertile. This is the only other mark you have to make on your calendar. During this time, you do not have to take any extra precautions during marriage relations. So you may mark this on the calendar with an I for infertile, a Y for Yellow, or any other way you might choose to mark it.
Just to recap, only two marks are needed on your calendar.
Mark the beginning of your period on the calendar with a large red dot.
Count 20 days out and put a second different mark (such as a Y for yellow) to show when you are infertile. If your cycles are regular, during this yellow time, no contraceptives have to be used during marital relations.

In the picture, we have also indicated each section of time, but it is unnecessary to mark all this. Only the dot and the Y are necessary. However, in the picture, red indicates a 7-day menstrual period, green a 12-day fertile period followed by an infertile period marked with yellow.
And that is the simplicity of natural family planning. It is certainly much healthier than pharmaceutical contraceptives and their many side effects.
Happy Family Planning!
"Consider what I say; and the Lord give thee understanding in all things." 2 Timothy 2:7