In conjunction to optional fasting days in haram (respected) months, we fast in days according to sunnah such as Monday or Thursday. We may also fast like Daud (David). I would like to share some personal practices. It might varies according to interpretations, traditions and customs.
I don't know if some people would accuse this as bida'ah but this is what I believe and I learned from pious creatures of Allah which is His prophets and messengers with the help of teachers, Quran, and Hadiths. If it does not in accordance to sunnah, I seek refuge to Allah from deviating may Allah forgive me and please pray for me to be saved from torments in the hereafter. I am still repenting on my sins for being an infidel and had heard many upsetting things like threatens from people around that I would be send to hell, anyway.
When we fast we should try to avoid from being detected by others that we are fasting. It has moral values hidden behind. This is regarding optional fasting and cleanliness. The practice that we usually do is that we would apply some olive oil on our exposed skin, hair, and beard. This is the common practice when entering masjid, in celebration and performing salat too. Comb the hair, don't let it messy while fasting! Also use siwak (twig stick) or brushing the teeth while fasting is OK but don't swallow the toothpaste or drink the water while fasting!
We should not show that we are exhausted or feeling hungry and act normal as long as we are able to perform the fast. If people invite us to eat while fasting before mid-day, then just fulfill the invitation because this is just optional fast. We can fast again on other days to come in the week. Refrain telling people that we are fasting if we are able to do that, and smile always. While fasting we must be extremely patient.
Regarding cleanliness while performing fast from left, those three twigs that we call as miswak or natural toothbrush and the bottle consists of olive oil. Now we have many brands of olive oil for hair, skin, or for cooking. The twigs was initially a single twig but I cut it to three for convenience.
When fasting we would wake up early before the adzan (calling for prayer) of dawn prayer for sahur. Sahur means pre-dawn meal. It is a good time to make supplications and asking Allah's mercy or forgiveness. As for myself, I had practiced since my repentance to Allah and return to the path of His messengers. I would never talk about this if I am not practicing it. Breaking fast would be simple like tamr (dates), plain water, or simple bread maybe two or three slices would be sufficient for my size. The same thing for sahur. Just to survive for eight hours before breaking the fast after sunset prayer calling according to local time.
Don't forget to recite His holiest Name as it is our responsibility to remember Him. Say: "bismillahirrahmaanirraaheem" - with the Name of Allah the Most Merciful, the Most Beneficent when taking sahur and also when breaking the fast. Also pray and supplicate to Allah before sipping drink when breaking the fast. Allah always listen to His servants.
Basic things for penance from left tasbeeh (dzikr beads), ma'athurat kitaab, and glorious Quran. I know tisbeeh is not sunnah because it is tied with thread and it is preferable with fingers. Then use fingers if possible, not a big problem. I usually use fingers to count remembrance to Allah but when memorizing something like Quranic verses, I would use tasbeeh. The ma'athurat, we can get them from religious departments according to states. I have with me various ma'athurats and I memorized few. This blue ones is the possession of my late maternal grandfather issued by Perlis religious department and they are not wahhabi just Muslims! I'm using it for my late maternal grandfather hoping Allah would bless his soul with the knowledge that I get from the ma'athurat.
During fasting time, basically... what should we avoid?
1. No eating, smoking and drinking during fasting period beginning from sunrise to sunset.
2. No vanity acts, it includes in oral and thinking. For examples, no obscenity, no false words, no arguments, not to look at people around to avoid evil-thinking, no slandering, no backbiting, not to listen to vain things, and other evil acts according to common senses.
3. No sexual-intercourse or anything related to sexual desire while fasting.
4. Don't take pre-dawn meal too early. Maybe 18 minutes before dawn prayer would be OK.
5. No delaying breaking the fast, as soon as we hear the sunset adzan we could break our fast just drink some water at least if you are trying to catch congregational maghrib prayer service while performing optional fast because not all of people fast if it is not Ramadhan.
I don't know whether we have non-Muslim guests. They might want to learn about some Muslims practices from Muslim themselves. This is what some of us are practicing and not from the report by non-believers. I share it according to my own practices and my faith as far as I could recall. My service to tell everyone is done. I am out of the responsibility and non-Muslim don't have to be a Muslim to understand others.
I don't think that this is a must. I use to wear this when performing prayer services. It is called as skull-cap or thaaqiyyah. When I finished performed Hajj manasik (rituals), and performed tahallul in Holy Mecca. Mum asked me to put on this cap but I refused. Then she said that just you wait until bird poops on your head! And what she said happened without a minute to come. I am still stubborn when I return home after the holy season because I thought that I was still young. Now I'm growing older and older. I just can't believe that I am not 19 teenage boy anymore but a 25 years old man. How fast the time consuming us, ya Allahhhhhh!!! :( I gradually put this on while praying in the sacred places like masjid or when reciting Quran to respect Allah 'Azza wa Jalla. Mum said, wearing this cap is to remind us that we had already repent to Him and never try to repeat the same mistakes.
Respectable Salafi and Tablighi brothers who happen to drop by might also help those who are not apart of their organizations, jama'at or divisions in enlightening about the sunnah practices. I don't like to call myself according to division but only a Muslim and a lowly servant of Allah who seek His mercy but I would be honored to receive help from brothers and sisters in order to see Him.
Refrain from division if possible, but love each other. Remind every brother and sister in faith with care. Refrain from hurting their feeling and be polite to everyone. Let everyone receives salvation, blessings and mercy from Allah!
So, this is my sharing. How about brothers and sisters in faith? What do you prefer to observe during optional fasting? Share with me. Maybe I could also practice them in turn if it is according to sunnah as a form of penance and charity to Allah. May everyone receives His blessings for sharing. Sealed with prayers for mercy, peace and love for brothers and sisters.