Some things are hard to figure out without a second person there to point out mistakes and provide guidance. The issue is you are with yourself, your thoughts and your speeches a much larger portion of time than you are with someone who is smarter than you and wants to help you out.
Do not despair. Here are some methods and benchmarks you can employ to judge and improve your speeches on your own.
1. Record Yourself
I am not starting off with particularly novel advice, but it is still very effective. Helps with clarity and smoothing out clumsy delivery like no other. Attempting to flow yourself is not just a question of delivery. It also implicates how you structure and phrase your ideas which is much more substantive than the yes/no question of whether the judge can hear your words. If they are hard to write down the judge has less time to appreciate the full nuance of your argument.
2. Ask Why
When you write an extension of an argument ask yourself why the statement you wrote is true. If the reason is not contained in the statement or the very next sentence you have a problem. Comb the speech you have written asking why after everything you write. After all, it is what the judge will be asking themselves the entire time you are talking.
3. Pretend you are Having a Conversation
Sometimes speeches are too jargon-filled and technical. Sometimes they are too abstract, while other times they miss the forest for the trees. To refocus your efforts, one method is to pretend you are having a conversation with a person that you are trying to convince. Sometimes things in the moment are too distorted by debate conventions or technical line by line coverage.
But when you are preparing you want to have a simple and direct command of the issues at play. So what would a non-debate person who is evaluating your arguments think and care about? Most people care about how many arguments you have, types of proof, sources, etc. This will lead to bonuses like realizing you don't need to say "takes out" or "internal link" as much.
4. Numbers and Labels
This isn't really an internal dialogue thing like the last two, but I bet your speech doesn't have nearly enough numbering or labels for your arguments. It is more a yes/no question, but one people don't bother with enough despite its overwhelming potential to improve your speech.
5. When an Issue Comes Up Deal With it in One Place
It is generally always a better rule of thumb to fully unpack an issue in the first place it is applicable on the line by line and then say "dealt with above" on subsequent arguments. Instead of this, people often say they will deal with it later. Dealing with it later means you deal with it a little the first time, then you said that transition statement and you probably won't fully develop the necessary ideas when you get to it later (if you remember).
This is easy to operationalize. Are you splitting the explanation of an argument into too many discrete places on the line by line?
6. Offense vs Defense Phrasing
It is easy to make a responsive argument but water down its potency by poor phrasing. This happens the most in critical debates when disussing alternatives on the AFF or extending the link when NEG. You want to double check that the focus of your speech is being maintained on the end goal: saying your opponents' position is bad. There are many indirect ways people go about doing this instead of just being direct the whole time.
7. Are Your Arguments Couched in Terms of the Speech that Preceded Yours?
This obviously matters for every kind of speech, but there are two scenarios where this has a premium. One is the 2AC on the case. The other is being NEG vs a planless AFF. Both situations are prone to pre-scripted rants that contradict the other team, but don't necessarily clash. It is a better idea to write those general blocks and explanations of your position as more of a reminder than a script (and a way to internalize what you are arguing about). But when it comes to speeh time you always want to be speaking to the warrant behind your opponent's argument.
Saying "yes nuke terror, our evidence says thefts of material are high and ISIS said they want to do it" does extend your impact, but when the NEG's evidence said no delivery systems and lots of points of the plot can be foiled. . .you have not moved the needle very much.
I am Lincoln, retired debate coach . This site's purpose is to post my ramblings about policy debate.