Because that's what it's really about, isn't it... It's not that there are people who would call any critical said about Israel antisemitic...
1) Don't use the word "Jew" or "Judaism" in any form or shape. Don't refer to the Jews or anything Jewish at all.
(But then I can't speak of Israel!)
Of course you can. All that takes is understanding that Israel is a country. Just another state among the dozens of others. Not a Jewish state. A state. As simple as that.
When a state violates human rights, people's religion, ethnicity or identity is irrelevant. It doesn't matter if they identify themselves as Jews or Palestinians, or Muslims, or Arabs. The main point here is and should remain so - that a human being is violating another human being's rights.
2) Avoid generalization.
3) Don't start referring to history and historical events, especially events of which veracity is questionable. You might be 100% convinced of that one version of history is the right one, but if there are several versions of the same history circulating, avoid it. After all, if the violation of human rights is a violation, it will stand on itself, and doesn't need backup from similar events in history. In fact, referring to something like Sabra and Shatila makes your story less credible.
4) Don't speculate about their motifs, or intentions or possible agenda.
Even if you are convinced of that the Jews are trying to take over the world, that the Protocols of the Elders of Zion is a true documentary and a warning to the world about Jews, even if you believe that there is a Jewish block or Israel Lobby, or Zionist agenda, even when you are absolutely certain of that Israel is trying to kill all the Palestinians, or at least make their lives a living hell, so that they will give up and go die somewhere else.
5) Avoid the use of inflammatory words like murder, genocide, torture, terrorism, concentration camp, etc. Even if you are 100% certain of that a crime has been committed, one of the Western civilization's ground pillars is "innocent until proven guilty".
Also, it is much easier to actually listen to people who say "1000 children have lost their lives in the Israel-Palestine conflict" than "the murderous Zionist bastards have slaughtered 1000 innocent Palestinian children!!!"
In the first case I can focus on the horrible fact of 1000 lives being lost, and start working toward finding solutions to that not one more child needs to die.
In the second case I think "Oh, it's those people whining again... I'm sure there's not even one real victim, and if there was, that was probably killed by his/her own people." and have no whatsoever inclination to discuss with you.
Try to say something similar but about the other side. How much would YOU listen to a pro-Israeli saying "those dirty little terrorists have again caused the death of 1000 children" compared to a person saying "1000 children have lost their lives in the Israel-Palestine conflict".
In the Israel-Palestine discussion some words have become code words to include all the antisemitism, and should thus be avoided in order to avoid misconception (here being, that you are an antisemite), and those are Zionism, Israel lobby and IOF (Israeli Occupation Forces. The correct name of Israel's army is Israeli Defense Forces. You don't need to agree, just use the correct abbreviation.). (I can't remember more right now, but I will add them, when I encounter them.)
If you cannot say what you have to say without using these words, then what you have to say is probably not worth saying - or it's antisemitic... >:->
6) Say what you have to say by changing the words you use of states, nations, nationality, ethnicity, religion etc. from Israel, Jewish, Israeli, Jew, Judaism to something that you are very passionately for. Like Palestine, Palestinian, Arab, Muslim, and see how you would feel if someone pro-Israeli would say the same about Palestine and Palestinian. If you would feel OK with that version, OK with the chosen words etc. then say it. If you feel any uneasiness or suspicion, change some words.
Really, if you could say what you say about Israel-Palestine conflict about any other conflict on this planet (and there really are several going on all the time) without feeling that that way of saying things sounds prejudiced or bigoted or racist, go ahead. It probably is all clean of antisemitism.
But if you think the Israel-Palestine conflict is DIFFERENT than the rest of the conflicts on this planet, or that Israel is in any way DIFFERENT from all the other states on this planet, then you probably are at least somewhat antisemitic.
If you STILL find it hard to understand how to criticize Israel without antisemitism, here's more pointers: How to Criticize Israel Without Being Anti-Semitic