I can try, but there are multiple systems and ways of doing it. The chassidish system is very different. For me and my siblings, this is roughly how it works:
When are you ready: it depends. In the UK, young adults start to date way younger than in America. From 18, girls will start to look, and from 21 for guy. My American friends often don't start looking until their early 20s.
I was almost 19 when we started 'hearing suggestions'. Typically, people who know the girl or the boy will make a suggestion, if they think they have an idea of a match. This doesn't have to be a professional matchmaker. It is often better if it is not, because the person making the suggestion has knowledge of both the boy and the girl, so are better placed to think of ideas. Basically, it is networking. People will say 'what are you looking for', and you would say the things that are most important for you. Someone who wants to marry a boy who is learning will say they want a boy in learning. Because that has such a massive effect on how they set up and start their lives together for financial and spiritual reasons, this is a very important question. There' no point setting up a date between someone who wants a boy who is working and a girl who wants a guy in learning. They also ask where do you want to live, a lot of couples want to start off their marriage with a year or so learning in Israel, but many don't. Then personality - do they want someone more quiet, or outgoing, what value are important to them. My list was pretty straightforward: I wanted a mentch, who would be working, i.e. good character was the number 1 for me. Not aggressive, considerate, respectful, honest, easy going, flexible, needed to have a sense of humour. That's just me though. My cousin wanted a strong personality, someone driven and a bit fiery (she sound him lol).
I was happy to meet different types of people and see what gelled.
So people made suggestions, and my parents looked into them. That means they called up family and friends of the boy who have been given as references and try to get a feel for what he is like and whether he would be a good fit for me and whether they liked what they heard about him. If there are any major skeletons in the closet, they are likely to come out at this point.
The information is very detailed and you get a lot of it. Resumes are common now, (an American import I think), but I don't think they are particularly useful as they often say very similar thing (think personal statement for uni...)
The boys side meanwhile do the same. If both sides agree to meet, you then do dor yeshorim testing, to see if you are genetically compatible. Doing it before the couple meet means neither get emotionally involved and then find out they are genetically incompatible. I have a parent who is a tay sachs carrier, so I am very very grateful for this, as had I married another carrier, it would have had devastating consequences.
If that is successful, the couple arrange through the shadchan to meet. The shadchan is the matchmaker. This can be the friend or family maker who made the suggestion. They act as the go between at the beginning. It is usually a fairly short first date. My dh and I met and went out for drinks and then ended up chatting. It's supposed to be a relatively short first date, a getting to know you kind of thing. We hit it off like a house on fire and we were out for hours. Our second date was the next day, and we went again for drinks, then a walk and we were out 6 hours (my parents were having kittens because it would have been rude to message on the date so they had no idea how it was going! and 6 hours is very very long for a second date).
Anyway, you feedback to the shadchan after every date.If it is going well, you can switch to arranging dates between you. My husband and I were fairly unusual in that we were both each other's first. When dating, the point is to see several thing; are you attracted to each other (very important), do you like each other/get on (for obvious reason!) and do your goals and values align. Some couples do only a few dates and agree to get engaged, some take much longer. The more orthodox, the shorter the dating period tends to be (UK, I mean, Americans take much much longer).
I went out on 5 dates over a two week period and I was the one to take the lead in getting engaged to my husband (ADHD impulsivity, I liked him and couldn't wait any longer, but that is not usual).
My parents were involved in that they researched my husband, suggestions went to them originally, but I could nix any I didn't like. i also discussed my dates heavily with them (and my girlfriends). I have a lot of trust in their judgment and an excellent relationship with my parents.
It's an arranged date, not an arranged marriage. The choice was entirely mine.
One of my siblings went out with a lot of girls for year before he found his DW.
What would rule a guy out? Depends on the girl, but for me, past girls friends, I was shomer negia which meant I don't touch members of the opposite sex outside my family, so a guy who was more modern and had dated and had experience with girls was out. Any drug use, alcohol addiction or smoking would be an instant no for me. Medical issues are also considered.
Things like how much secular exposure they have or want is considered, e.g. for me I was happy to meet a guy who watched films, but didn't go to the cinema (I can't explain the nuances atm), I listened to non Jewish music so he had to be ok with a girl who did that, what he wears/what I wear. Basically, you are trying to match up people who are at similar levels of religious observance; it would have been a waste of time for me to go out with someone who only wore black hat and white shirt/black trousers all week, and would learn all day and didn't want films in the house, because we would not be on the same page religiously.
Converts have a harder time with shidduchim for sure. More because of social reasons. It takes a strong character to become an Orthodox Jewish convert, and they are often quite a bit older, so it's already harder to find a shidduch when you are older, and they often need someone a bit out of the box. Children of converts I think to a lesser degree, and it depends on what community they are in. My friend is the daughter of a convert, and she and her sister were both married very young, I don't think either had any problem.
Lineage is called yichus, and it is about whether a) you have big Ravs (Rabbi's who are spiritual leaders ) or Rebbes (chassidish spiritual leaders) in your direct ancestry, and also b) whether you come from an unbroken chain of religious orthodox Jews - it varies by community how important it is. To chassidim, it is uber important. In yeshivish circles (another group of chareidi Jew) it can be quite important, but maybe not to the same degree. In some circles yichus is almost like royalty.
Yichus was totally unimportant to me, my inlaws are both baalei teshuva (people who became frum/religious/orthodox when they were older), and are two of the loveliest, kindest, most generous people you will ever meet. I also really respect that they became religious, it is not an easy path.
There are also professional shadchan services, but I will leave that to someone else!