For someone who, for whatever reason, will not participate in selichot, are there any alternatives (things to say, acts to do etc.) suggested to properly prepare for the high holidays?
ELiyahu Ki Tov in Sefer Hatoda'ah (Book of Heritage) mentions that Elul is am "Et Ratzon" - a time of "acceptance"/ Therefore, this is an appropriate month to concentrate on Teshuva. Saying Selichot and increasing supplications is one means of doing this, but, going through the motions of saying the words of Selichot without feeling anything or encouraging Teshuva, at least minimally, would miss the point.
Ramba"m, among others, has written a detailed volume on how to perform Teshuva. The main concept is to inspect your deeds, regret past sins and resolve to improve.
However, I think an excellent exercise is to view some of the "Al Chet" prayer of Yom Kippur. While I am not an Art Scroll enthusiast, in general (too long to explain why, now), the back of their Yom Kippur machzor (Ashkenaz or Sefarad - would have the same thing) has a long explanation of the "Ashamnu" and "Al Chet" in English. You should read and think about what it says, there. It points out many nuances of various sins that you normally would say, "Oh, I never do this", but, in fact, you probably do.
Now, after you look at this section, resolve and try during the next week through Yom Kippur and even beyond to try to improve yourself in even 1 aspect per day. Keep in mind that the word "chet" doesn't really mean "doing something wrong". It means, "missing the mark". G-d expects you to live up to your full potential. Have you done that? Perhaps, not. So improving yourself is far more important than mouthing the words of Selichot if they don't mean anything.
(Yasher Koach to @DoubleAA, except that he was far more concise.)
This is the month of Elul so repent, repent, and repent. Think of any words that hurt others, actions that were not right and beg forgiveness. Turn from the sins and do not do them any more( very important).
If you do not have a community you can celebrate online with the "7 beggars synagogue" website, they broadcast live every Shabbat and holidays live streaming online for those who are sick, homebound or traveling and do not have a community
They have been on the air live for 7 years now and never miss a shabbat
Just google "7 beggars synagogue" the live stream starts Shabbat Fridays 8:00pm Est Saturday Shabbat 10 am and check for High Holidays
The screen is blank until a service starts but they never miss a broadcast live.